常規閉包變量增量

Question

如果我正在讀取文件的每一行，如下所示

file.eachLine {line->
println line
}

是否可以讀取閉包內部的NEXT行。

例如

file.eachLine {line ->
//print next line as well if current line contains 'hooray'
if (line.find(/hooray/)!=null)
{
   println "current line: ${line}"
   println "next line: ${line->next}" //this is just my syntax...
}
}

Answer 1

閉包並不直接支持這一點，但是如果您稍作改動，很容易實現相同的邏輯：

// test script:
def f = new File("test.txt")
def currentLine
f.eachLine { nextLine ->
    if (currentLine) {
        if (currentLine.find(/hooray/)) {
            println "current line: ${currentLine}"
            println "next line: ${nextLine}"
        }    
    }    
    currentLine = nextLine
}


// test.txt contents:
first line
second line
third line
fourth line
fifth hooray line 
sixth line
seventh line

編輯：

如果您正在尋找Chili在下面評論的封裝，則可以始終在File上定義自己的方法：

File.metaClass.eachLineWithNextLinePeek = { closure ->
    def currentLine
    delegate.eachLine { nextLine ->
        if (currentLine) {
            closure(currentLine, nextLine) 
        }
        currentLine = nextLine
    }
}

def f = new File("test.txt")
f.eachLineWithNextLinePeek { currentLine, nextLine ->
    if (currentLine.find(/hooray/)) {
        println "current line: ${currentLine}"
        println "next line: ${nextLine}"
     }
}