Ruby - lambda 与 Proc.new [英] Ruby - lambda vs. Proc.new

问题描述

可能重复:
proc和lambda有什么区别红宝石?

当运行这个 Ruby 代码时:

When run this Ruby code:

def func_one
    proc_new = Proc.new {return "123"}
    proc_new.call
    return "456"
end

def func_two
    lambda_new = lambda {return "123"}
    lambda_new.call
    return "456"
end

puts "The result of running func_one is " + func_one
puts ""
puts "The result of running func_two is " + func_two

我得到的结果如下:

The result of running func_one is 123

The result of running func_two is 456

至于func_two，firstreturn的值在哪里，即123?

As for func_two, where is the the value of the first return, that is, 123?

谢谢.

推荐答案

这是 Procs 和 lambdas 之间的主要区别之一.

This is one of the main differences between Procs and lambdas.

Proc 中的 return 从其封闭的块/方法返回，而 lambda 中的 return 只是从 lambda 返回.当你在 func_two 中调用 lambda 时，它只是简单地返回它的值，而不是保存.

A return in a Proc returns from its enclosing block/method, while a return in a lambda simply returns from the lambda. When you call the lambda inside the func_two, it simply returns its value in place, which is not saved.

在此处阅读 Procs v. lambdas:http://en.wikibooks.org/wiki/Ruby_Programming/Syntax/Method_Calls

Read on Procs v. lambdas here: http://en.wikibooks.org/wiki/Ruby_Programming/Syntax/Method_Calls

查看重复的 SO 问题:为什么显式返回会对 Proc 产生影响?

See duplicate SO question: Why does explicit return make a difference in a Proc?

为了进一步说明这种差异，将 func_one 和 func_two 换成块，看看会发生什么:

To further illustrate this difference, swap func_one and func_two for blocks and see what happens:

> begin; lambda { return 1 }.call end
1
> begin; Proc.new { return 1 }.call end
LocalJumpError: unexpected return
...

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