(&:id)在Product.all.map(&:id)中到底做了什么 [英] What exactly does (&:id) do in Product.all.map(&:id)

问题描述

这是我想要绕过的代码行:

Here's the line of code I'm trying to wrap my head around:

Category.all.map(&:id).each { |id| Category.reset_counters(id, :products) }

希望某人可以帮助我了解(&:id)的功能以及它如何影响其余部分?我相信它会将符号:id转换为会响应id的 proc ?！?但这会令人困惑...

Hoping someone can help me understand what (&:id) is doing and how it impacts the rest of the line? I believe it turns the symbol :id into a proc that'll respond to id?!? But then it gets confusing...

提前谢谢！

推荐答案

Category.all.map(&:id)

是

Category.all.map { |a| a.id }

关于它如何影响其余的行，以上部分将所有id值作为单个Array返回.然后，将这个Array id传递给另一个对each的调用，该调用将每个id迭代地传递给reset_counters.

as for how it affects the rest of the line, the above section returns all id values as a single Array. This Array of ids is then passed into another call to each, which iteratively passes each id into reset_counters.

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