在Grunt任务中使用节点模块失败 [英] Using a node module within a Grunt Task fails

问题描述

正在执行： node test.js 这个档案：

  var exif = require（'exif2'）; 
 
 exif（'fixtures / forest.png'，function（err，o）{
 console.log（arguments）; 
}）; 
  

生成预期的输出

执行grunt进程： grunt projectJSON

  module.exports = function（grunt）{
 var exif = require（'exif2'）; 
 return grunt.registerMultiTask（projectJSON，创建项目JSON文件，function（）{
 exif（'fixtures / forest.png'，function（err，o）{
 console.log（arguments）; 
}）; 
}）; 
 
} 
  

**注意，我只是用 fixtures / forest.png 文件

不产生任何输出。这个回调甚至没有被解雇。

当我使用console.log exif时，我得到：[Function]

我错过了什么？我认为这不起作用是因为任务繁重，但我不知道如何解决它。将它包装在try-catch块中不会产生任何结果。

解决方案

您需要使 projectJSON 任务异步 - Grunt在调用exif回调之前退出。

查看关于异步任务的Grunt文档

这就是你如何使任务异步：

  module.exports = function（grunt）{
 var exif = require（'exif2'）; 
 
 grunt.registerMultiTask（projectJSON，创建项目JSON文件，function（）{
 //使任务异步
 var done = this.async（） ; 
 
 exif（'fixtures / forest.png'，function（err，o）{
 console.log（arguments）; 
 
 //调用任务回调继续
 //其他Grunt任务
 done（）; 
}）; 
}）; 
 
} 
  

I'm trying to extract meta data from files read within a Grunt task.

executing: node test.js on this file:

var exif = require('exif2');

exif('fixtures/forest.png', function (err, o) {
    console.log(arguments);
});

Produces the expected output

However, executing the grunt process: grunt projectJSON

module.exports = function (grunt) {
    var exif = require('exif2');
    return grunt.registerMultiTask("projectJSON", "Creates project JSON file.", function () {
        exif('fixtures/forest.png', function (err, o) {
            console.log(arguments);
        });
    });

}

** note that I am just testing with the fixtures/forest.png file

Produces no output whatsoever. The callback isn't even fired.

When I console.log exif, I get: [Function]

What am I missing? I think that the doesn't work is because of the grunt task, but I have no idea how to fix it. Wrapping it in a try-catch block produces nothing.

解决方案

You need to make your projectJSON task asynchronous - Grunt is exiting before your exif callback is being invoked.

Have a look at the Grunt documentation on asynchronous tasks.

This is how you can make your task asynchronous:

module.exports = function (grunt) {
    var exif = require('exif2');

    grunt.registerMultiTask("projectJSON", "Creates project JSON file.", function () {
        // Make task asynchronous.
        var done = this.async();

        exif('fixtures/forest.png', function (err, o) {
            console.log(arguments);

            // Invoke the task callback to continue with
            // other Grunt tasks.
            done();
        });
    });

}

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