如何在 Rails 3 的 build_association 调用中传递多个构造函数参数？
build_foo 调用中的第二个参数永远不会进入 Foo#initialize （即 args[1] 是 nil）。有什么建议可以将两个或多个参数传递到 Foo#initialize 中，同时保持 *args 作为唯一要初始化的参数？
class Foo < ActiveRecord::Base
belongs_to :bar
def initialize *args
super()
self.total = args[0] + args[1]
end
end
class Bar < ActiveRecord::Base
has_one :foo
def do_something
build_foo 2, 3 # 3 never reaches Foo#initialize
build_foo [2,3] # args[0] == [2,3], which is not what's desired
save!
end
end
The second argument in the build_foo call never makes it into Foo#initialize (i.e. args[1] is nil). Any suggestions so as to get two or more arguments passed into Foo#initialize while keeping *args the only argument to initialize?
class Foo < ActiveRecord::Base
belongs_to :bar
def initialize *args
super()
self.total = args[0] + args[1]
end
end
class Bar < ActiveRecord::Base
has_one :foo
def do_something
build_foo 2, 3 # 3 never reaches Foo#initialize
build_foo [2,3] # args[0] == [2,3], which is not what's desired
save!
end
end
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回答你的问题——你不能。仅仅是因为 build_foo 在文档，即
arguments = {}，因此您应该只传递参数哈希来初始化新记录。另外，您不需要在
#initialize中调用#super，因为 AR::Base 本身没有定义#initialize。为什么您需要传递2个不同的参数而不是参数散列？位置参数不会告诉您设置了哪个值，并且对于 AR 对象，表中可能有多个属性。
To answer your question - you can't. Simply because build_foo has only one parameter defined in documentation, which is
arguments = {}, so you should pass there only arguments hash to initialize your new record.Also you don't need to call
#superin#initialize, as AR::Base doesn't define#initializeitself.Why do you need to pass 2 distinct arguments instead of arguments hash? Positional arguments doesn't tell you which value you set, and with AR objects you probably has more than one attribute in table.