你能摆脱 Groovy 的“每个"吗?关闭? [英] Can you break from a Groovy "each" closure?

问题描述

是否可以从 Groovy .each{Closure} 中break，还是应该使用经典循环?

Is it possible to break from a Groovy .each{Closure}, or should I be using a classic loop instead?

推荐答案

不，你不能在不抛出异常的情况下中止每个".如果您希望在特定条件下中断中断，您可能需要经典循环.

Nope, you can't abort an "each" without throwing an exception. You likely want a classic loop if you want the break to abort under a particular condition.

或者，您可以使用find"闭包而不是 each 并在您休息时返回 true.

Alternatively, you could use a "find" closure instead of an each and return true when you would have done a break.

此示例将在处理整个列表之前中止:

This example will abort before processing the whole list:

def a = [1, 2, 3, 4, 5, 6, 7]

a.find { 
    if (it > 5) return true // break
    println it  // do the stuff that you wanted to before break
    return false // keep looping
}

打印

1
2
3
4
5

但不打印 6 或 7.

but doesn't print 6 or 7.

使用接受闭包的自定义中断行为编写自己的迭代器方法也非常容易:

It's also really easy to write your own iterator methods with custom break behavior that accept closures:

List.metaClass.eachUntilGreaterThanFive = { closure ->
    for ( value in delegate ) {
        if ( value  > 5 ) break
        closure(value)
    }
}

def a = [1, 2, 3, 4, 5, 6, 7]

a.eachUntilGreaterThanFive {
    println it
}

也打印:

1
2
3
4
5    

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