Question

我是承诺的新手，我想从类中返回数据作为承诺。我有两个类，每个类有两个函数。我正在做的每个函数都是从类中返回一个promise，但是我无法执行promise.all。以下是代码

Class1

class TestClass {

    firstPromise() {
        return new Promise((resolve, reject) => {
            resolve('return first promise')
        })
    }

    secondPromise() {
        return new Promise((resolve, reject) => {
            resolve('return second promise')
        })
    }
}
module.exports.TestClass = TestClass;

Class2

class TestClass1 {

    firstPromise() {
        return new Promise((resolve, reject) => {
            resolve('return first promise')
        })
    }

    secondPromise() {
        return new Promise((resolve, reject) => {
            resolve('return second promise')
        })
    }
}
module.exports.TestClass1 = TestClass1;

Main function
    let data = req.body;
    let test1Object;
    let testObject;
    let testParam;
    let testParam1;
    if (data.hasOwnProperty('param1')) {
        test1Object = new test1.TestClass1();
        test1Object.firstPromise().then((data)=>{
            testParam1 = test1Object.secondPromise();
        });
    }
    if (data.hasOwnProperty('param2')) {
        testObject = new test.TestClass();
        testObject.firstPromise().then((data)=>{
            testParam = testObject.secondPromise()
        });
    }
    Promise.all([testParam,testParam1]).then((data)=>{
       console.log(data)
    });

显示 [未定义，未定义]

Answer 1

当您执行Promise.all()时，承诺尚未解决，因此testParam和testParam1为undefined。我认为你应该将第一个承诺分配给testParam1：

testParam1 = test1Object.firstPromise().then(data => test1Object.secondPromise());

，同样是第二个testParam：

testParam = testObject.firstPromise().then(data => testObject.secondPromise());

Promise.all不显示数据

1 个答案: