仅在方法完成后继续循环

Question

我希望以下代码同步运行。 每个inquirer.prompt() 需要一个接一个地运行。

这是我现在的代码：

_.forEach(diff.wrongVersion, (dependency) => {
    choices = [ 'project version: ' + dependency.projectVersion, 'layer version: ' + dependency.layerVersion];
    inquirer.prompt({
        type: 'list',
        name: 'dependencies',
        message: 'Choose which version to use for ' + dependency.name,
        choices
    });
});

有人可以帮我解决这个问题吗？

我认为这可以通过 Promise 完成，但我不知道如何。

Answer 1

如果我理解正确的话，你需要以下原则：

var inquirer = {};

inquirer.prompt = function(object) {
    return new Promise(function(resolve, reject) {
    setTimeout(function() { // <-- here I emulate async execution
      console.log('object ==> ', object);
      resolve();
    }, 1000);
  });
}

var diff = {
  wrongVersion: [{
    projectVersion: 0,
    layerVersion: 0,
    name: 'zero'
  }, {
    projectVersion: 1,
    layerVersion: 1,
    name: 'one'
  }, {
    projectVersion: 2,
    layerVersion: 2,
    name: 'two'
  }, {
    projectVersion: 3,
    layerVersion: 3,
    name: 'three'
  }]
}

var iterator = 0;

function callPrompt() {
  var dependency = diff.wrongVersion[iterator];

  var choices = ['project version: ' + dependency.projectVersion, 'layer version: ' + dependency.layerVersion];

  inquirer.prompt({
    type: 'list',
    name: 'dependencies',
    message: 'Choose which version to use for ' + dependency.name,
    choices: choices
  }).then(function() {
    iterator++;

    if (diff.wrongVersion[iterator]) {
        callPrompt();
    }
  });
};

callPrompt();

jsfiddle 示例（注意 concole）-https://jsfiddle.net/regwtew1/2/

Answer 2

您可以使用Array#reduce或lodash#reduce来实现这种顺序提示。

diff.wrongVersion.reduce((promise, dependency) => promise.then(result =>

    inquirer.prompt({
        type: 'list',
        name: dependency.name,
        message: `Choose which version to use for: ${dependency.name}`,
        choices: [
            `project version: ${dependency.projectVersion}`,
            `layer version: ${dependency.layerVersion}`
        ]
    })

    .then(answer => Object.assign(result, answer))

), Promise.resolve({})).then(result => {
    console.log(result);
});

// =========== Mocking Inquirer Module =====================
var inquirer = {
  prompt: function(question) {
    var choices = question.choices
      .map((v, i) => `[${i+1}] - ${v}`)
      .join('\n');
    var message = `${question.message}\n${choices}`;
    var result = {};
    var answer;
    
    return new Promise((resolve, reject) => {
    
      do {
        answer = parseInt(window.prompt(message));
      } while(
        isNaN(answer) || 
        answer < 1 || 
        answer > choices.length || 
        answer === null
      );
      
      if(answer === null) {
        reject();
      } else {
        result[question.name] = question.choices[answer-1];
        resolve(result);
      }
      
    });
    
  }
};

const diff = {
	wrongVersion: [
		{
			projectVersion: 'pv-1.0',
			layerVersion: 'lv-1.0',
			name: 'Dep-A'
		},
		{
			projectVersion: 'pv-1.0',
			layerVersion: 'lv-1.0',
			name: 'Dep-B'
		},
		{
			projectVersion: 'pv-1.0',
			layerVersion: 'lv-1.0',
			name: 'Dep-C'
		},
		{
			projectVersion: 'pv-1.0',
			layerVersion: 'lv-1.0',
			name: 'Dep-D'
		},
		{
			projectVersion: 'pv-1.0',
			layerVersion: 'lv-1.0',
			name: 'Dep-E'
		},
	]
};


diff.wrongVersion.reduce((promise, dependency) => promise.then(result =>

	inquirer.prompt({
		type: 'list',
		name: dependency.name,
		message: `Choose which version to use for: ${dependency.name}`,
		choices: [
			`project version: ${dependency.projectVersion}`,
			`layer version: ${dependency.layerVersion}`
		]
	})

	.then(answer => Object.assign(result, answer))

), Promise.resolve({})).then(result => {
	console.log(result);
});