ActiveRecord::Associations::CollectionProxy - Ruby on Rails 繁體中文

<<(*records) 連結

透過將其外來金鑰設定到關聯的主鍵，將一個或多個記錄新增到集合中。由於<< 會展平其引數清單並插入每個記錄，因此push 和 concat 的行為相同。傳回self，因此可以串連多個追加。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.size # => 0
person.pets << Pet.new(name: 'Fancy-Fancy')
person.pets << [Pet.new(name: 'Spook'), Pet.new(name: 'Choo-Choo')]
person.pets.size # => 3

person.id # => 1
person.pets
# => [
#      #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#      #<Pet id: 2, name: "Spook", person_id: 1>,
#      #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

別名亦為：push、append、concat

來源：顯示 | 在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 1049
def <<(*records)
  proxy_association.concat(records) && self
end

==(other) 連結

等同於 Array#==。如果兩個陣列包含相同數量的元素，且每個元素都等於 other 陣列中的對應元素，則傳回 true，否則傳回 false。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets
# => [
#      #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#      #<Pet id: 2, name: "Spook", person_id: 1>
#    ]

other = person.pets.to_ary

person.pets == other
# => true

請注意，未持續化的記錄仍可能視為等於

other = [Pet.new(id: 1), Pet.new(id: 2)]

person.pets == other
# => true

來源：顯示 | 在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 980
def ==(other)
  load_target == other
end

any?() 連結

如果集合不為空，則傳回 true。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.count # => 0
person.pets.any?  # => false

person.pets << Pet.new(name: 'Snoop')
person.pets.count # => 1
person.pets.any?  # => true

當集合尚未載入時未經過濾就直接呼叫等於 collection.exists?。若你最後還是會載入集合，那麼呼叫 collection.load.any? 會比較好，可以避免額外的查詢。

你也可以傳入一個 block 來定義標準。行為會是一樣的，若根據標準所篩選出來的集合不為空值，則回傳 true。

person.pets
# => [#<Pet name: "Snoop", group: "dogs">]

person.pets.any? do |pet|
  pet.group == 'cats'
end
# => false

person.pets.any? do |pet|
  pet.group == 'dogs'
end
# => true

來源：在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 836

append(*records) 連結

別名：<<

build(attributes = {}, &block) 連結

傳回一個集合類型的物件，該物件已被指派 attributes，並且與這個物件連結，但尚未儲存。你可以傳入由屬性雜湊組成的陣列，這會傳回一個包含新物件的陣列。

class Person
  has_many :pets
end

person.pets.build
# => #<Pet id: nil, name: nil, person_id: 1>

person.pets.build(name: 'Fancy-Fancy')
# => #<Pet id: nil, name: "Fancy-Fancy", person_id: 1>

person.pets.build([{name: 'Spook'}, {name: 'Choo-Choo'}, {name: 'Brain'}])
# => [
#      #<Pet id: nil, name: "Spook", person_id: 1>,
#      #<Pet id: nil, name: "Choo-Choo", person_id: 1>,
#      #<Pet id: nil, name: "Brain", person_id: 1>
#    ]

person.pets.size  # => 5 # size of the collection
person.pets.count # => 0 # count from database

別名為：new

來源：顯示 | 在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 318
def build(attributes = {}, &block)
  @association.build(attributes, &block)
end

calculate(operation, column_name) 連結

來源：顯示 | 在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 724
def calculate(operation, column_name)
  null_scope? ? scope.calculate(operation, column_name) : super
end

clear() 連結

等同於 delete_all。不同的地方是傳回的是 self，而不是包含已刪除物件的陣列，因此可以串連方法。有關詳細資訊，請參閱 delete_all。請注意，由於 delete_all 是透過直接執行 SQL 查詢到資料庫中來移除記錄，因此物件的 updated_at 欄位並未變更。

來源：顯示 | 在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 1066
def clear
  delete_all
  self
end

concat(*records) 連結

別名：<<

count(column_name = nil, &block) 連結

計數所有記錄。

class Person < ActiveRecord::Base
  has_many :pets
end

# This will perform the count using SQL.
person.pets.count # => 3
person.pets
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

傳遞一個區塊將在 SQL 選擇一個人的所有寵物，然後使用 Ruby 執行計數。

person.pets.count { |pet| pet.name.include?('-') } # => 2

來源：在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 733

create(attributes = {}, &block) 連結

傳回一個集合類型的物件，該物件已被指派屬性，連結到這個物件，且已經儲存（如果它通過驗證）。

class Person
  has_many :pets
end

person.pets.create(name: 'Fancy-Fancy')
# => #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>

person.pets.create([{name: 'Spook'}, {name: 'Choo-Choo'}])
# => [
#      #<Pet id: 2, name: "Spook", person_id: 1>,
#      #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.size  # => 3
person.pets.count # => 3

person.pets.find(1, 2, 3)
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

來源：顯示 | 在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 349
def create(attributes = {}, &block)
  @association.create(attributes, &block)
end

create!(attributes = {}, &block) 連結

與 create 相似，但如果記錄無效，會擲回例外。

class Person
  has_many :pets
end

class Pet
  validates :name, presence: true
end

person.pets.create!(name: nil)
# => ActiveRecord::RecordInvalid: Validation failed: Name can't be blank

來源：顯示 | 在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 365
def create!(attributes = {}, &block)
  @association.create!(attributes, &block)
end

delete(*records) 連結

根據 `:dependent` 選項指定的策略從集合中刪除所提供的 `records`。若未給定 `:dependent` 選項，將採用預設策略。傳回已刪除記錄的陣列。

`has_many :through` 關聯的預設刪除策略為 `:delete_all`。

`has_many` 關聯的預設刪除策略為 `:nullify`。這會將外來鍵設為 `NULL`。

class Person < ActiveRecord::Base
  has_many :pets # dependent: :nullify option by default
end

person.pets.size # => 3
person.pets
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.delete(Pet.find(1))
# => [#<Pet id: 1, name: "Fancy-Fancy", person_id: 1>]

person.pets.size # => 2
person.pets
# => [
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

Pet.find(1)
# => #<Pet id: 1, name: "Fancy-Fancy", person_id: nil>

若設為 `:destroy`，將呼叫所有 `records` 的 `destroy` 方法來刪除。詳細資訊請參閱 `destroy`。

class Person < ActiveRecord::Base
  has_many :pets, dependent: :destroy
end

person.pets.size # => 3
person.pets
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.delete(Pet.find(1), Pet.find(3))
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.size # => 1
person.pets
# => [#<Pet id: 2, name: "Spook", person_id: 1>]

Pet.find(1, 3)
# => ActiveRecord::RecordNotFound: Couldn't find all Pets with 'id': (1, 3)

若設為 `:delete_all`，將 **不** 呼叫所有 `records` 的 `destroy` 方法而刪除。

class Person < ActiveRecord::Base
  has_many :pets, dependent: :delete_all
end

person.pets.size # => 3
person.pets
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.delete(Pet.find(1))
# => [#<Pet id: 1, name: "Fancy-Fancy", person_id: 1>]

person.pets.size # => 2
person.pets
# => [
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

Pet.find(1)
# => ActiveRecord::RecordNotFound: Couldn't find Pet with 'id'=1

你可以傳入 `Integer` 或 `String` 值，它會找出對應於 `id` 的記錄並對其執行刪除動作。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.size # => 3
person.pets
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.delete("1")
# => [#<Pet id: 1, name: "Fancy-Fancy", person_id: 1>]

person.pets.delete(2, 3)
# => [
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

來源：顯示 | 在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 620
def delete(*records)
  @association.delete(*records).tap { reset_scope }
end

delete_all(dependent = nil) 連結

根據 `:dependent` 選項指定的策略從集合中刪除所有記錄。若未給定 `:dependent` 選項，將採用預設策略。

`has_many :through` 關聯的預設刪除策略為 `:delete_all`。

`has_many` 關聯的預設刪除策略為 `:nullify`。這會將外來鍵設為 `NULL`。

class Person < ActiveRecord::Base
  has_many :pets # dependent: :nullify option by default
end

person.pets.size # => 3
person.pets
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.delete_all
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.size # => 0
person.pets      # => []

Pet.find(1, 2, 3)
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: nil>,
#       #<Pet id: 2, name: "Spook", person_id: nil>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: nil>
#    ]

`has_many` 和 `has_many :through` 依賴項的預設策略為 `:delete_all`，若 `:dependent` 選項設為 `:destroy`。記錄不會執行實體化，也不會觸發任何回呼。

class Person < ActiveRecord::Base
  has_many :pets, dependent: :destroy
end

person.pets.size # => 3
person.pets
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.delete_all

Pet.find(1, 2, 3)
# => ActiveRecord::RecordNotFound: Couldn't find all Pets with 'id': (1, 2, 3)

若設為 `:delete_all`，將 **不** 呼叫物體的 `destroy` 方法而刪除。

class Person < ActiveRecord::Base
  has_many :pets, dependent: :delete_all
end

person.pets.size # => 3
person.pets
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.delete_all

Pet.find(1, 2, 3)
# => ActiveRecord::RecordNotFound: Couldn't find all Pets with 'id': (1, 2, 3)

來源：顯示 | 在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 474
def delete_all(dependent = nil)
  @association.delete_all(dependent).tap { reset_scope }
end

destroy(*records) 連結

刪除所提供的 `records`，並將它們從集合中移除。此方法會總是從資料庫中移除記錄，忽略 `:dependent` 選項。傳回已刪除記錄的陣列。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.size # => 3
person.pets
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.destroy(Pet.find(1))
# => [#<Pet id: 1, name: "Fancy-Fancy", person_id: 1>]

person.pets.size # => 2
person.pets
# => [
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.destroy(Pet.find(2), Pet.find(3))
# => [
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.size  # => 0
person.pets       # => []

Pet.find(1, 2, 3) # => ActiveRecord::RecordNotFound: Couldn't find all Pets with 'id': (1, 2, 3)

你可以傳入 `Integer` 或 `String` 值，它會找出對應於 `id` 的記錄，再從資料庫中將它們刪除。

person.pets.size # => 3
person.pets
# => [
#       #<Pet id: 4, name: "Benny", person_id: 1>,
#       #<Pet id: 5, name: "Brain", person_id: 1>,
#       #<Pet id: 6, name: "Boss",  person_id: 1>
#    ]

person.pets.destroy("4")
# => #<Pet id: 4, name: "Benny", person_id: 1>

person.pets.size # => 2
person.pets
# => [
#       #<Pet id: 5, name: "Brain", person_id: 1>,
#       #<Pet id: 6, name: "Boss",  person_id: 1>
#    ]

person.pets.destroy(5, 6)
# => [
#       #<Pet id: 5, name: "Brain", person_id: 1>,
#       #<Pet id: 6, name: "Boss",  person_id: 1>
#    ]

person.pets.size  # => 0
person.pets       # => []

Pet.find(4, 5, 6) # => ActiveRecord::RecordNotFound: Couldn't find all Pets with 'id': (4, 5, 6)

來源：顯示 | 在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 692
def destroy(*records)
  @association.destroy(*records).tap { reset_scope }
end

destroy_all() 連結

直接從資料庫中刪除集合中的記錄，忽略 `:dependent` 選項。記錄會實體化，並呼叫 `before_remove`、`after_remove`、`before_destroy` 和 `after_destroy` 回呼。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.size # => 3
person.pets
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.destroy_all

person.pets.size # => 0
person.pets      # => []

Pet.find(1) # => Couldn't find Pet with id=1

來源：顯示 | 在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 501
def destroy_all
  @association.destroy_all.tap { reset_scope }
end

distinct(value = true) 連結

指定記錄是否應該是獨特的。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.select(:name)
# => [
#      #<Pet name: "Fancy-Fancy">,
#      #<Pet name: "Fancy-Fancy">
#    ]

person.pets.select(:name).distinct
# => [#<Pet name: "Fancy-Fancy">]

person.pets.select(:name).distinct.distinct(false)
# => [
#      #<Pet name: "Fancy-Fancy">,
#      #<Pet name: "Fancy-Fancy">
#    ]

來源：在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 697

empty?() 連結

如果集合為空，傳回 `true`。如果集合已載入，等同於 `collection.size.zero?`。如果集合未載入，等同於 `!collection.exists?`。如果集合尚未載入，而且你會擷取記錄，最好檢查 `collection.load.empty?`。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.count  # => 1
person.pets.empty? # => false

person.pets.delete_all

person.pets.count  # => 0
person.pets.empty? # => true

來源：顯示 | 在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 831
def empty?
  @association.empty?
end

fifth() 連結

與 first 相同，但僅傳回第 5 筆記錄。

來源：在 GitHub 中

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 201

find(*args) 連結

在集合中找出回應著 id 的物件。使用與 ActiveRecord::FinderMethods.find 相同的規則。如果找不到物件，傳回 ActiveRecord::RecordNotFound 錯誤。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.find(1) # => #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>
person.pets.find(4) # => ActiveRecord::RecordNotFound: Couldn't find Pet with 'id'=4

person.pets.find(2) { |pet| pet.name.downcase! }
# => #<Pet id: 2, name: "fancy-fancy", person_id: 1>

person.pets.find(2, 3)
# => [
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

來源：顯示 | 在 GitHub 中

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 138
def find(*args)
  return super if block_given?
  @association.find(*args)
end

first(limit = nil) 連結

從集合中傳回第一筆記錄，或前 n 筆記錄。如果集合為空，第一個形式會傳回 nil，而第二個形式會傳回一個空陣列。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.first # => #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>

person.pets.first(2)
# => [
#      #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#      #<Pet id: 2, name: "Spook", person_id: 1>
#    ]

another_person_without.pets          # => []
another_person_without.pets.first    # => nil
another_person_without.pets.first(3) # => []

來源：在 GitHub 中

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 144

forty_two() 連結

與 first 相同，但僅傳回第 42 筆記錄。又稱為取得「reddit」。

來源：在 GitHub 中

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 209

fourth() 連結

與 first 相同，但僅傳回第 4 筆記錄。

來源：在 GitHub 中

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 193

include?(record) 連結

如果給定的 record 出現在集合中，傳回 true。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets # => [#<Pet id: 20, name: "Snoop">]

person.pets.include?(Pet.find(20)) # => true
person.pets.include?(Pet.find(21)) # => false

來源：顯示 | 在 GitHub 中

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 927
def include?(record)
  !!@association.include?(record)
end

last(limit = nil) 連結

從集合中傳回最後一筆記錄，或最後 n 筆記錄。如果集合為空，第一個形式會傳回 nil，而第二個形式會傳回一個空陣列。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.last # => #<Pet id: 3, name: "Choo-Choo", person_id: 1>

person.pets.last(2)
# => [
#      #<Pet id: 2, name: "Spook", person_id: 1>,
#      #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

another_person_without.pets         # => []
another_person_without.pets.last    # => nil
another_person_without.pets.last(3) # => []

來源：顯示 | 在 GitHub 中

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 259
def last(limit = nil)
  load_target if find_from_target?
  super
end

length() 連結

在目標上呼叫 size，傳回集合的大小。如果集合已載入，length 和 size 是相等的。如果集合尚未載入而你將需要這些記錄，這個方法會使用較少的查詢。否則，size 的效率較高。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.length # => 3
# executes something like SELECT "pets".* FROM "pets" WHERE "pets"."person_id" = 1

# Because the collection is loaded, you can
# call the collection with no additional queries:
person.pets
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

來源：在 GitHub 中

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 787

load_target() 連結

來源：顯示 | 在 GitHub 中

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 44
def load_target
  @association.load_target
end

loaded() 連結

別名為：loaded?

loaded?() 連結

如果關聯已經載入，傳回 true，否則傳回 false。

person.pets.loaded? # => false
person.pets.records
person.pets.loaded? # => true

也別名為：loaded

來源：顯示 | 在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 53
def loaded?
  @association.loaded?
end

many?() 連結

如果集合有多筆記錄，傳回 true。等同於 collection.size > 1。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.count # => 1
person.pets.many? # => false

person.pets << Pet.new(name: 'Snoopy')
person.pets.count # => 2
person.pets.many? # => true

你也可以傳遞 block 來定義標準。行為一致，如果基於標準的集合有多筆記錄，傳回 true。

person.pets
# => [
#      #<Pet name: "Gorby", group: "cats">,
#      #<Pet name: "Puff", group: "cats">,
#      #<Pet name: "Snoop", group: "dogs">
#    ]

person.pets.many? do |pet|
  pet.group == 'dogs'
end
# => false

person.pets.many? do |pet|
  pet.group == 'cats'
end
# => true

來源：在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 877

new(attributes = {}, &block) 連結

別名為：build

pluck(*column_names) 連結

來源：顯示 | 在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 728
def pluck(*column_names)
  null_scope? ? scope.pluck(*column_names) : super
end

proxy_association() 連結

傳回集合的關聯物件。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.proxy_association
# => #<ActiveRecord::Associations::HasManyAssociation owner="#<Person:0x00>">

傳回與 person.association(:pets) 相同的物件，讓你進行呼叫例如 person.pets.proxy_association.owner。

更多資訊，請參閱 Associations::ClassMethods 中的關聯擴充。

來源：顯示 | 在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 944
def proxy_association
  @association
end

push(*records) 連結

別名：<<

reload() 連結

從資料庫重新載入集合。傳回 self。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets # fetches pets from the database
# => [#<Pet id: 1, name: "Snoop", group: "dogs", person_id: 1>]

person.pets # uses the pets cache
# => [#<Pet id: 1, name: "Snoop", group: "dogs", person_id: 1>]

person.pets.reload # fetches pets from the database
# => [#<Pet id: 1, name: "Snoop", group: "dogs", person_id: 1>]

來源：顯示 | 在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 1085
def reload
  proxy_association.reload(true)
  reset_scope
end

replace(other_array) 連結

使用 other_array 取代此集合。這會執行變更偵測，並僅刪除/新增已變更的記錄。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets
# => [#<Pet id: 1, name: "Gorby", group: "cats", person_id: 1>]

other_pets = [Pet.new(name: 'Puff', group: 'celebrities')]

person.pets.replace(other_pets)

person.pets
# => [#<Pet id: 2, name: "Puff", group: "celebrities", person_id: 1>]

如果提供的陣列的關聯類型不正確，它會引發 ActiveRecord::AssociationTypeMismatch 錯誤

person.pets.replace(["doo", "ggie", "gaga"])
# => ActiveRecord::AssociationTypeMismatch: Pet expected, got String

來源：顯示 | 在 GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 391
def replace(other_array)
  @association.replace(other_array)
end

reset() 連結

卸載關聯。傳回 self。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets # fetches pets from the database
# => [#<Pet id: 1, name: "Snoop", group: "dogs", person_id: 1>]

person.pets # uses the pets cache
# => [#<Pet id: 1, name: "Snoop", group: "dogs", person_id: 1>]

person.pets.reset # clears the pets cache

person.pets  # fetches pets from the database
# => [#<Pet id: 1, name: "Snoop", group: "dogs", person_id: 1>]

Source: show | on GitHub

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 1106
def reset
  proxy_association.reset
  proxy_association.reset_scope
  reset_scope
end

scope() 連結

傳回此關聯中記錄的 Relation 物件

Source: show | on GitHub

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 949
def scope
  @scope ||= @association.scope
end

second() 連結

與 first 相同，但只傳回第二條記錄。

Source: on GitHub

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 177

second_to_last() 連結

與 last 相同，但只傳回倒數第二條記錄。

Source: on GitHub

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 226

**select(*fields, &block)** 連結

有兩種作用方式。

第一：指定從結果集中選取的欄位子集合。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.select(:name)
# => [
#      #<Pet id: nil, name: "Fancy-Fancy">,
#      #<Pet id: nil, name: "Spook">,
#      #<Pet id: nil, name: "Choo-Choo">
#    ]

person.pets.select(:id, :name)
# => [
#      #<Pet id: 1, name: "Fancy-Fancy">,
#      #<Pet id: 2, name: "Spook">,
#      #<Pet id: 3, name: "Choo-Choo">
#    ]

請小心，因為這也表示您正在初始化只有您所選欄位的模型物件。如果您嘗試存取不在初始化記錄中的欄位（id 除外），您會收到

person.pets.select(:name).first.person_id
# => ActiveModel::MissingAttributeError: missing attribute 'person_id' for Pet

第二：您可以傳遞一個區塊，以便可像 Array#select 一樣使用。這會為範圍建置一個來自資料庫的物件陣列，將它們轉換成陣列並使用 Array#select 來進行反覆運算。

person.pets.select { |pet| /oo/.match?(pet.name) }
# => [
#      #<Pet id: 2, name: "Spook", person_id: 1>,
#      #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

Source: on GitHub

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 59

size() 連結

傳回集合大小。如果集合尚未載入，它會執行 SELECT COUNT(*) 查詢。否則，它會呼叫 collection.size。

如果集合已經載入，則 size 和 length 相等。如果沒有，而您無論如何都需要記錄，則 length 會進行一次較少的查詢。否則 size 會比較有效率。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets.size # => 3
# executes something like SELECT COUNT(*) FROM "pets" WHERE "pets"."person_id" = 1

person.pets # This will execute a SELECT * FROM query
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.size # => 3
# Because the collection is already loaded, this will behave like
# collection.size and no SQL count query is executed.

Source: show | on GitHub

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 782
def size
  @association.size
end

take(limit = nil) 連結

根據與 ActiveRecord::FinderMethods.take 相同規則，提供集合中的記錄（如果提供參數則為 N 條記錄）。

class Person < ActiveRecord::Base
  has_many :pets
end

person.pets
# => [
#       #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#       #<Pet id: 2, name: "Spook", person_id: 1>,
#       #<Pet id: 3, name: "Choo-Choo", person_id: 1>
#    ]

person.pets.take # => #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>

person.pets.take(2)
# => [
#      #<Pet id: 1, name: "Fancy-Fancy", person_id: 1>,
#      #<Pet id: 2, name: "Spook", person_id: 1>
#    ]

another_person_without.pets         # => []
another_person_without.pets.take    # => nil
another_person_without.pets.take(2) # => []

Source: show | on GitHub

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 289
def take(limit = nil)
  load_target if find_from_target?
  super
end

target() 連結

Source: show | on GitHub

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 40
def target
  @association.target
end

third() 連結

與 first 相同，但只傳回第三筆記錄。

來源： GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 185

third_to_last() 連結

與 last 相同，但只傳回第三筆最後的記錄。

來源： GitHub 上

# File activerecord/lib/active_record/associations/collection_proxy.rb, line 218

類別 ActiveRecord::Associations::CollectionProxy < Relation

Active Record 集合 Proxy

執行個體公開方法

<<(*records) 連結

==(other) 連結

any?() 連結

append(*records) 連結

build(attributes = {}, &block) 連結

calculate(operation, column_name) 連結

clear() 連結

concat(*records) 連結

count(column_name = nil, &block) 連結

create(attributes = {}, &block) 連結

create!(attributes = {}, &block) 連結

delete(*records) 連結

delete_all(dependent = nil) 連結

destroy(*records) 連結

destroy_all() 連結

distinct(value = true) 連結

empty?() 連結

fifth() 連結

find(*args) 連結

first(limit = nil) 連結

forty_two() 連結

fourth() 連結

include?(record) 連結

last(limit = nil) 連結

length() 連結

load_target() 連結

loaded() 連結

loaded?() 連結

many?() 連結

new(attributes = {}, &block) 連結

pluck(*column_names) 連結

proxy_association() 連結

push(*records) 連結

reload() 連結

replace(other_array) 連結

reset() 連結

scope() 連結

second() 連結

second_to_last() 連結

select(*fields, &block) 連結

size() 連結

take(limit = nil) 連結

target() 連結

third() 連結

third_to_last() 連結

**select(*fields, &block)** 連結