读取所有文件后,使用async模块触发回调

Question

我正在使用caolan的'async'模块打开一个文件名数组(在本例中是模板文件名).

根据文档,我正在使用async.forEach(),所以我可以在所有操作完成后触发回调.

一个简单的测试用例是:

var async = require('async')
var fs = require('fs')

file_names = ['one','two','three'] // all these files actually exist

async.forEach(file_names, 
    function(file_name) {
        console.log(file_name)
        fs.readFile(file_name, function(error, data) {
            if ( error) {   
                console.log('oh no file missing')   
                return error
            } else {
                console.log('woo '+file_name+' found')
            }       
        })
    }, function(error) {
        if ( error) {   
            console.log('oh no errors!')
        } else {
            console.log('YAAAAAAY')
        }
    }
)

输出如下:

one
two
three
woo one found
woo two found
woo three found

即,似乎最终的回调没有解雇.我需要做什么才能使最终的回调发生火灾？

Answer 1

正在所有项目上运行的函数必须进行回调,并将其结果传递给回调.请参阅下文(我还将fileName分开以提高可读性):

var async = require('async')
var fs = require('fs')

var fileNames= ['one','two','three']


// This callback was missing in the question.
var readAFile = function(fileName, callback) {
    console.log(fileName)
    fs.readFile(fileName, function(error, data) {
        if ( error) {   
            console.log('oh no file missing')   
            return callback(error)
        } else {
            console.log('woo '+fileName+' found')
            return callback()
        }       
    })
}

async.forEach(fileNames, readAFile, function(error) {
    if ( error) {   
        console.log('oh no errors!')
    } else {
        console.log('YAAAAAAY')
    }
})

返回:

one
two
three
woo one found
woo two found
woo three found
YAAAAAAY