promise.then()和promise.catch()在节点程序中不起作用

Question

我正在尝试显示一个由opencv4nodejs读取并由人脸识别模块处理的实时流。问题是，promise.then((不起作用。甚至在相应的条件下都没有catch((。(我是node的新手，并承诺。(预期工作流程：

从网络摄像头读取帧(通过cv.read(->保存到缓冲区(通过cv.imwrite(->从缓冲区读取帧(根据fr.loadImage(->处理(通过detecter.locateFaces(->显示->重复处理。

const fr = require('face-recognition');
const cv = require('opencv4nodejs');
const events = require('events');
const detector = fr.FaceDetector()
const cap = new cv.VideoCapture(0);
const win = new fr.ImageWindow()
const eventEmitter = new events.EventEmitter();
function process(){
console.log('process');
return new Promise(function(resolve,reject){
console.log('promise');
var frame = cap.read();
cv.imwrite(`${__dirname}/buffer/img.jpg`, frame);
if(frame != null)
resolve('resolve');
else
reject('Problem While reading');
});
}
eventEmitter.on('read',function(string){
console.log('event call');
var promise = process();
promise.then(function(string){
console.log(string);
const image = fr.loadImage(`${__dirname}/buffer/img.jpg`);
const faceRectangles = detector.locateFaces(image);
win.setImage(image);
fr.hitEnterToContinue();
}).catch(function(err){
console.log(err);
});
});
while(true){
console.log('emit');
eventEmitter.emit('read','abcd');
}
/*****expected output should be*****
emit
event call
process
promise
resolve
/*****getting output*****
emit
event call
process
promise
*/

Answer 1

由于您使用的是eventEmitter，您的代码应该如下所示：

const fr = require('face-recognition');
const cv = require('opencv4nodejs');
const events = require('events');
const Promise = require('bluebird');
const detector = fr.FaceDetector()
const cap = new cv.VideoCapture(0);
const win = new fr.ImageWindow()
const eventEmitter = new events.EventEmitter();
function process(){
console.log('process');
return new Promise(function(resolve,reject) {
console.log('promise');
var frame = cap.read();
cv.imwrite(`${__dirname}/buffer/img.jpg`, frame);
if(frame != null)
resolve();
else
reject('Problem While reading');
});
}
eventEmitter.on('read',function(string){
console.log('event call');
var promise = process();
promise.then(function(string){
console.log(string);
const image = fr.loadImage(`${__dirname}/buffer/img.jpg`);
const faceRectangles = detector.locateFaces(image);
win.setImage(image);
fr.hitEnterToContinue();
}).catch(function(err){
console.log(err);
});
});
while(true){
console.log('emit');
eventEmitter.emit('read','abcd');
}

Answer 2

const fr = require('face-recognition');
const cv = require('opencv4nodejs');
const events = require('events');
const detector = fr.FaceDetector()
const cap = new cv.VideoCapture(0);
const win = new fr.ImageWindow()
const eventEmitter = new events.EventEmitter();
function process(){
console.log('process');
return new Promise(function(resolve,reject){
console.log('promise');
var frame = cap.read();
cv.imwrite(`${__dirname}/buffer/img.jpg`, frame);
if(frame != null)
resolve('resolve');
else
reject('Problem While reading');
});
}
eventEmitter.on('read',function(string){
console.log('event call');
var promise = process();
console.log(promise);
promise.then(function(string){
console.log(string);
const image = fr.loadImage(`${__dirname}/buffer/img.jpg`);
const faceRectangles = detector.locateFaces(image);
console.log(faceRectangles);
win.setImage(image);
// fr.hitEnterToContinue();
eventEmitter.emit('read','abcd');
}).catch(function(err){
console.log(err);
});
});
eventEmitter.emit('read','abcd');

更改：1( 从eventEmitter.emit('read','abcd');中删除while循环2(promise.then()中的递归发射事件我观察到，当连续发出promise.then((事件时，它不起作用，所以我发出promise.then((中的事件，所以现在它工作得很好。