Node.js猫鼬-如何避免回调地狱? [英] Nodejs Mongoose - how to avoid callback hell?

问题描述

使用Mongoose一段时间后，我可能做错了.当您有太多回调时，我发现很难阅读，例如:

I might be doing it wrong with Mongoose after using it for a while. I find it difficult to read when you have too much callbacks, eg:

我想找到一个文档并进行更新.我需要先找到它，然后update将位于findOne的回调中.

I want to find a document and update it. I need to find it first, then the update will be inside the callback of the findOne.

var sam = new Character({ name: 'Sam', inventory: {}});

Character.findOne({ name: 'Sam' }, function(err, character) {
      console.log(character);

      // now I want to update it.
      character.update({... }, function(err, characterID) {

          // now I want to know the size of the document after the update.
          Character.findOne({ _id: characterID }, function(err, character) {
            // Now update it again....
        });
    });

});

它最终以意大利面代码结尾！

It ends up a spaghetti code eventually!

你明白我的意思吗?

有什么想法可以做得更好吗?

Any ideas how to do it better?

在没有所有这些回调的情况下，mongodb native会更好吗?

Or mongodb native is better without all these callbacks?

Character.findOne({...}, function(err, character) {

    return character.update(...);

}).select("-field1 -field2").then(function(data) {
      //
}).catch(function(error) {
    // Handle any error from all above steps
}).done();

错误:

TypeError: Character.findOne(...).select(...).then(...).catch(...).done is not a function

推荐答案

您可以在nodejs中使用 q promise的链接

You can use chaining of q promise in nodejs

var Q = require('q');

function findOne(filter) {
    return Q.Promise(function(resolve, reject) {
        Character.findOne(filter, function(err, character) {
            resolve({
                err: err,
                character: character
            });
        });
    });
}

function update(data) {
    return Q.Promise(function(resolve, reject) {
        character.update(data, function(err, characterID) {
            resolve({
                err: err,
                characterID: characterID
            });
        });
    });
}

findOne({ name: 'Sam' }).then(function(data) {
    if (!data.err) {
        // now you can update it.
        return update(data.character);
    } else {
        throw new Error(data.err);
    }
}).then(function(data) {
    if (!data.err) {
        // now you can update it.
        return update(data.characterId);
    } else {
        throw new Error(data.err);
    }
    return findOne({ id: characterId });
}).then(function(data) {
    if (!data.err) {
        // now you can update it.
        return update(data.character);
    } else {
        throw new Error(data.err);
    }
}).catch(function(error) {
    // Handle any error from all above steps
}).done();

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