我正在努力学习一门有几个功能的课程。他们每个人都会返回一个承诺。
我的问题是，在第一次返回Promise之后，下一个函数中的this-reference不是类对象而是全局节点对象。
以下是一些示例代码：
index.js：
"use strict";
const debug = require("./dbg.js");
const testClass = require("./testClass.js");
const dbg = new debug();
const tc = new testClass(dbg);
tc.printTestMessage()
.then(tc.Test1)
.then(tc.Test2)
.then(tc.Test3);
testClass.js：
"use strict";
const Promise = require("bluebird");
let testClass = function(dbg) {
let self = this;
self._dbg = dbg;
};
testClass.prototype.printTestMessage = function() {
let self = this;
return new Promise(function(resolve) {
self._dbg.printDebug(3, "testClass - printTestMessage", "start printing...");
setTimeout(function() {
self._dbg.printDebug(3, "testClass - printTestMessage", "finished printing...");
resolve();
}, 2000);
});
};
testClass.prototype.Test1 = function() {
let self = this;
return new Promise(function(resolve) {
self._dbg.printDebug(3, "testClass - Test1", "start printing...");
setTimeout(function() {
self._dbg.printDebug(3, "testClass - Test1", "finished printing...");
resolve();
}, 2000);
});
};
testClass.prototype.Test2 = function() {
let self = this;
return new Promise(function(resolve) {
self._dbg.printDebug(3, "testClass - Test2", "start printing...");
setTimeout(function() {
self._dbg.printDebug(3, "testClass - Test2", "finished printing...");
resolve();
}, 2000);
});
};
testClass.prototype.Test3 = function() {
let self = this;
return new Promise(function(resolve) {
self._dbg.printDebug(3, "testClass - Test3", "start printing...");
setTimeout(function() {
self._dbg.printDebug(3, "testClass - Test3", "finished printing...");
resolve();
}, 2000);
});
};
module.exports = testClass;
有关如何将每个函数粘贴到类引用的任何帮助吗？
答案 0 :(得分：-1)
自己找到它：每个新的Promise都必须在最后添加.bind（self）。
例如：
testClass.prototype.Test3 = function() {
let self = this;
return new Promise(function(resolve) {
self._dbg.printDebug(3, "testClass - Test3", "start printing...");
setTimeout(function() {
self._dbg.printDebug(3, "testClass - Test3", "finished printing...");
resolve();
}, 2000);
}).bind(self); //<-- this is the important part
};