如何使用Groovy的正则表达式获取部分匹配的布尔值? [英] How do I get a Boolean value for a partial match using Groovy's regex?

问题描述

Groovy具有正则表达式匹配运算符"(==~). 文档表示它返回布尔值，但需要严格匹配".它没有定义严格匹配".

Groovy has a regular expression "match operator" (==~). The documentation says it returns a Boolean, but requires a "strict match". It does not define "strict match".

我不熟悉此表达式为false的任何正则表达式系统.但是，这就是Groovy告诉我的.

I'm not familiar with any regex system where this expression is false. But, that's what Groovy is telling me.

'foo-bar-baz' ==~ /bar/ // => false

find运算符(=~)返回一个Matcher，显然可以为匹配和捕获组建立索引.但是，我必须编写一个显式测试才能使该表达式返回布尔值.

The find operator (=~) returns a Matcher, which can be indexed for matches and capture groups, apparently. But, I'd have to write an explicit test to have this expression return a Boolean.

('foo-bar-baz' =~ /bar/)[0] != null // => true

两个问题...

1. 什么是严格匹配"?
2. 如何在不向表达式中添加大量垃圾的情况下获取布尔值?

推荐答案

'foo-bar-baz' ==~ /bar/等于"foo-bar-baz".matches("bar")，也就是说，它需要完整的字符串匹配.

The 'foo-bar-baz' ==~ /bar/ is equal to "foo-bar-baz".matches("bar"), that is, it requires a full string match.

=~运算符允许 partial 匹配，也就是说，它可以在字符串内找到一个或多个匹配项.

The =~ operator allows partial match, that is, it may find a match/matches inside a string.

因此:

println('foo-bar-baz' ==~ /bar/) // => false
println('bar' ==~ /bar/)         // => true
println('foo-bar-baz' =~ /bar/)  // => java.util.regex.Matcher[pattern=bar region=0,11 lastmatch=]

参见此 Groovy演示

如果需要检查部分匹配项，则无法避免构建 Matcher 对象:

If you need to check for a partial match, you cannot avoid building a Matcher object:

使用查找运算符=~构建 java.util.regex.Matcher 实例

use the find operator =~ to build a java.util.regex.Matcher instance

   def text = "some text to match"
   def m = text =~ /match/                                           
   assert m instanceof Matcher                                       
   if (!m) {                                                         
       throw new RuntimeException("Oops, text not found!")
   }

if (!m)等同于调用if (!m.find())

或者，您可以两次使用!将结果强制转换为正确的布尔值:

Alternatively, you may use the ! twice to cast the result to correct Boolean value:

println(!!('foo-bar-baz' =~ /bar/))

返回 true .

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