如何将数组作为单独的参数传递给方法答案

【问题标题】：How to pass array as separated arguments to method如何将数组作为单独的参数传递给方法
【发布时间】：2013-08-23 07:37:06
【问题描述】：

这似乎接近我需要的，但它不适合我。

Achieving `call_user_func_array` in Ruby

我有一个常量列表

TYPE = %w(:groups :projects)

我在我的相关列表模型上使用https://github.com/brainspec/enumerize，它有

enumerize :list_type, in: %w(groups projects), scope: :type

所以根据 github 页面上的文档，

RelatedList.type(:groups) # returns all RelatedList of type 'groups'

但是，我想获取我的常量 TYPE 中包含的所有相关列表

所以我尝试了

RelatedList.type(TYPE) # doesn't work
RelatedList.send(:type, TYPE) # doesn't work
RelatedList.send(:type, *TYPE) # doesn't work.

RelatedList.type 需要一个单独的参数列表作为符号，但我拥有的是一个符号数组。

我如何做到这一点？

根据下面回答中的 DNNX 请求，这是完整的回溯。

NoMethodError: undefined method `value' for nil:NilClass
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/bundler/gems/enumerize-bc01a5cb3c79/lib/enumerize/activerecord.rb:34:in `block (2 levels) in _define_scope_methods!'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/bundler/gems/enumerize-bc01a5cb3c79/lib/enumerize/activerecord.rb:34:in `map'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/bundler/gems/enumerize-bc01a5cb3c79/lib/enumerize/activerecord.rb:34:in `block in _define_scope_methods!'
    from (irb):2
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/commands/console.rb:90:in `start'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/commands/console.rb:9:in `start'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus/rails.rb:134:in `console'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:116:in `block in command'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:103:in `fork'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:103:in `command'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:80:in `block (3 levels) in go'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:80:in `fork'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:80:in `block (2 levels) in go'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:73:in `each'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:73:in `block in go'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:62:in `loop'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:62:in `go'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:78:in `block (3 levels) in go'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:78:in `fork'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:78:in `block (2 levels) in go'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:73:in `each'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:73:in `block in go'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:62:in `loop'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:62:in `go'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:78:in `block (3 levels) in go'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:78:in `fork'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:78:in `block (2 levels) in go'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:73:in `each'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:73:in `block in go'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:62:in `loop'
    from /Users/kw/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/gems/zeus-0.13.3/lib/zeus.rb:62:in `go'

【问题讨论】：

标签： ruby-on-rails ruby ruby-on-rails-4

【解决方案1】：

... 我拥有的是一个符号数组

不，不是。这个TYPE = %w(:groups :projects) 是由两个字符串':groups' 和':projects' 组成的数组，而不是符号数组。

试试这个：

TYPE = %w(groups projects)
RelatedList.type(*TYPE)

或者，如果您很幸运并且在 Ruby 2.0.0 上运行您的应用，请使用符号数组字面量：

TYPE = %i(groups projects)
#=> [:groups, :projects]

【讨论】：

为什么不%i(groups projects)？
我得到 NoMethodError: undefined method `value' for nil:NilClass RelatedList.type(:groups, :projects) 工作正常。
不。即使使用符号数组，它也不起作用。 rb(main):002:0> RelatedList.type(TYPE) NoMethodError: undefined method `value' for nil:NilClass from /Users/shivam/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/bundler/gems/enumerize-bc01a5cb3c79/lib/enumerize/activerecord.rb:34:in `block (2 levels) in _define_scope_methods!' from /Users/shivam/.rbenv/versions/2.0.0-p247/lib/ruby/gems/2.0.0/bundler/gems/enumerize-bc01a5cb3c79/lib/enumerize/activerecord.rb:34:in `map'
RelatedList.type(*TYPE) 效果很好！您可以将其发布为答案吗？你也可以简单解释一下*TYPE背后的魔力是什么？我的意思是它基本上是什么？
@DNNX 如果 TYPE 在类 Content 中定义，*TYPE 如何工作。即，我只能直接调用 Content::TYPE 而不是 TYPE。我试过 *Content::TYPE 和 Content::*TYPE 但它们都失败了。