Ruby 注入初始值是一个哈希值 [英] Ruby inject with initial being a hash

问题描述

谁能告诉我为什么会出现以下情况:

Can any one tell me why the following:

['a', 'b'].inject({}) {|m,e| m[e] = e }

抛出错误:

IndexError: string not matched
        from (irb):11:in `[]='
        from (irb):11:in `block in irb_binding'
        from (irb):11:in `each'
        from (irb):11:in `inject'
        from (irb):11
        from C:/Ruby192/bin/irb:12:in `<main>'

而以下有效?

a = {}
a["str"] = "str"

推荐答案

你的区块需要返回累积的哈希值:

Your block needs to return the accumulating hash:

['a', 'b'].inject({}) {|m,e| m[e] = e; m }

相反，它在第一次传递后返回字符串 'a'，在下一次传递中它变成 m 并且您最终调用字符串的 []= 方法.

Instead, it's returning the string 'a' after the first pass, which becomes m in the next pass and you end up calling the string's []= method.

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