在Ruby中动态设置局部变量 [英] Dynamically set local variables in Ruby

问题描述

我对在Ruby中动态设置局部变量感兴趣.不创建方法，常量或实例变量.

I'm interested in dynamically setting local variables in Ruby. Not creating methods, constants, or instance variables.

所以像这样:

args[:a] = 1
args.each_pair do |k,v|
  Object.make_instance_var k,v
end
puts a
> 1

我想要局部变量，特别是因为所讨论的方法存在于模型中，并且我不想污染全局空间或对象空间.

I want locally variables specifically because the method in question lives in a model and I dont want to pollute the global or object space.

推荐答案

此处的问题是each_pair中的块具有不同的作用域.在其中分配的任何局部变量将只能在其中访问.例如，这:

The problem here is that the block inside each_pair has a different scope. Any local variables assigned therein will only be accessible therein. For instance, this:

args = {}
args[:a] = 1
args[:b] = 2

args.each_pair do |k,v|
  key = k.to_s
  eval('key = v')
  eval('puts key')
end

puts a

产生此:

1
2
undefined local variable or method `a' for main:Object (NameError)

为了解决这个问题，您可以创建一个本地哈希，为该哈希分配密钥，然后在其中访问它们，就像这样:

In order to get around this, you could create a local hash, assign keys to this hash, and access them there, like so:

args = {}
args[:a] = 1
args[:b] = 2

localHash = {}
args.each_pair do |k,v|
  key = k.to_s
  localHash[key] = v
end

puts localHash['a']
puts localHash['b']

当然，在此示例中，它只是复制带有键字符串的原始哈希.我假设实际用例更加复杂.

Of course, in this example, it's merely copying the original hash with strings for keys. I'm assuming that the actual use-case, though, is more complex.

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