从被调用函数的回调函数中访问函数变量

Question

这是我的代码，它的所有工作都是return_info没有得到安装的例外。是否可以从请求函数调用的回调中访问父return_info变量？

module.exports = { 
    fetch_template_by_id : function(id) { 
    var request = require('request'); 
    var return_info = {}; //TO BE MODIFIED 
    request('http://localhost:5000/templates/v1/template/' + id, function (error, response, body) { 
     if (!error && response.statusCode == 200) { 
     console.log("Success - Error = " + error + " | Response = " + response + " | Body = " + body); 
     return_info.body = body;     // Should Modify the top 
     return_info.json = JSON.parse(body);  // Should Modify the top 
     return_info.success = true;    // Should Modify the top 
     } else { 
     console.error("There was an error requesting template ID=" + id) 
     return_info.error = error;    // Should Modify the top 
     return_info.response = response;   // Should Modify the top 
     return_info.success = false;    // Should Modify the top 
     } 
    }); 
    return return_info; 
    } 
} 

编辑：进一步参考这是调用它的代码。

app.get('/form', function (req, res) { 
var template_helper = require('../services/template-helper'); 
var template = template_helper.fetch_template_by_id("BirthRecord"); 
console.log(template); 
if (template.success === true) { 
    res.render('form', {"template": template.json }); 
} else { 
    res.render('index'); 
} 
}); 

Answer 1

由于请求是异步的，它会在您返回return_info后执行。所以，你需要提供以下

module.exports = { 
    fetch_template_by_id : function(id, cb) { 
    var request = require('request'); 
    var return_info = {}; //TO BE MODIFIED 
    request('http://localhost:5000/templates/v1/template/' + id, function (error, response, body) { 
     if (!error && response.statusCode == 200) { 
     console.log("Success - Error = " + error + " | Response = " + response + " | Body = " + body); 
     return_info.body = body;     // Should Modify the top 
     return_info.json = JSON.parse(body);  // Should Modify the top 
     return_info.success = true;    // Should Modify the top 
     } else { 
     console.error("There was an error requesting template ID=" + id) 
     return_info.error = error;    // Should Modify the top 
     return_info.response = response;   // Should Modify the top 
     return_info.success = false;    // Should Modify the top 
     } 
     cb(return_info); 
    }); 
    } 
} 

fetch_template_by_id('awesome', function (info) { 
    console.log(info); 
}); 

编辑回调函数作为展示 - 随着上下文

你需要沿着回调的方式想，如果你想开始工作的Node.js ，下面是你应该怎么做的例子。

app.get('/form', function (req, res) { 
    var template_helper = require('../services/template-helper'); 
    template_helper.fetch_template_by_id("BirthRecord", function (template) { 
    console.log(template); 
    if (template.success === true) { 
     res.render('form', {"template": template.json }); 
    } else { 
     res.render('index'); 
    } 
    }); 
});