Question

如何在Rails中有条件地将哈希添加到*args数组？如果存在原始值，我不想踩踏原始值。

例如，我有一个接收数组的方法：

def foo(*args)
  # I want to insert {style: 'bar'} into args but only if !style.present?
  bar(*args)                              # do some other stuff 
end

我已经开始使用rails提供的extract_options和reverse_merge方法：

def foo(*args)
  options = args.extract_options!         # remove the option hashes
  options.reverse_merge!  {style: 'bar'}  # modify them
  args << options                         # put them back into the array
  bar(*args)                              # do some other stuff 
end

它有效，但看起来很冗长，而且不是很红宝石。我觉得我错过了什么。

Answer 1

是的，#extract_options!是在Rails中实现它的方法。如果你想要更优雅，你必须使用别名，或者找到你自己的方式来处理这个需求，或者由已经完成它的人搜索gem。

Answer 2

参加聚会有点晚-但是如果您需要定期进行此操作，则值得为此使用一些实用程序方法-例如类似于以下内容，它将options哈希合并为args-ary-并负责将其与可能存在的hash-args合并，或者仅在不存在哈希的情况下将其追加为新哈希args：

def merge_into_args!(opts={}, *args)
  opts.each do |key, val|
    if args.any?{|a| a.is_a?(Hash)}
      args.each{|a| a.merge!(key => val) if a.is_a?(Hash)}
    else
      args << {key => val}
    end
  end

  args
end

如果您想将修改后的options哈希合并回*args并将它们传递给另一种方法，例如：

 # extract options from args
 options = args.extract_options!

 # modify options
 # ...
 # ...

 # merge modified options back into args and use them as args in another_method
 args = merge_into_args!(options,*args)
 another_method(*args)

 # or as 1-liner directly in the method call:
 another_method(*merge_into_args!(options,*args))

 # and in your case you can conditionally modify the options-hash and merge it 
 # back into the args in one go like this:
 another_method(*merge_into_args!(options.reverse_merge(style: 'bar'),*args))

更多示例：

# args without hash 
args = ["first", "second"]

# merge appends hash
args = merge_into_args!({ foo: "bar", uk: "zok" },*args)
#=> ["first", "second", {:foo=>"bar", :uk=>"zok"}]

# Another merge appends the new options to the already existing hash:   
args = merge_into_args!({ ramba: "zamba", halli: "galli" },*args)
#=> ["first", "second", {:foo=>"bar", :uk=>"zok", :ramba=>"zamba", :halli=>"galli"}]

# Existing options are updated accordingly when the provided hash contains
# identical keys:
args = merge_into_args!({ foo: "baz", uk: "ZOK!", ramba: "ZAMBA" },*args)
#=> ["first", "second", {:foo=>"baz", :uk=>"ZOK!", :ramba=>"ZAMBA", :halli=>"galli"}]

如何向* args添加哈希？

2 个答案: