7.5 Models -- Persisting Records

1、概述

1. 在Ember Data上以每一個實例爲基礎，records被持久化。在DS.Model的任何一個實例上調用save()而且它將產生一個網絡請求。

2. 下面是一些例子：

var post = store.createRecord('post', {
  title: 'Rails is Omakase',
  body: 'Lorem ipsum'
});

post.save(); // => POST to '/posts'

store.findRecord('post', 1).then(function(post) {
  post.get('title'); // => "Rails is Omakase"

  post.set('title', 'A new post');

  post.save(); // => PUT to '/posts/1'
});

2、Promises

1. save()返回一個promise，因此它是很是容易處理成功和失敗的狀況的。這裏是一個廣泛的模式：

var post = store.createRecord('post', {
  title: 'Rails is Omakase',
  body: 'Lorem ipsum'
});

var self = this;

function transitionToPost(post) {
  self.transitionToRoute('posts.show', post);
}

function failure(reason) {
  // handle the error
}

post.save().then(transitionToPost).catch(failure);

// => POST to '/posts'
// => transitioning to posts.show route

2. promises甚至使處理失敗的網絡請求變得容易：

var post = store.createRecord('post', {
  title: 'Rails is Omakase',
  body: 'Lorem ipsum'
});

var self = this;

var onSuccess = function(post) {
  self.transitionToRoute('posts.show', post);
};

var onFail = function(post) {
  // deal with the failure here
};

post.save().then(onSuccess, onFail);

// => POST to '/posts'
// => transitioning to posts.show route

3. 在這裏 here你能夠學到更多關於promises，可是這裏是另一個關於展現如何重試持久化的例子：

function retry(callback, nTimes) {
  // if the promise fails
  return callback().catch(function(reason) {
    // if we haven't hit the retry limit
    if (nTimes > 0) {
      // retry again with the result of calling the retry callback
      // and the new retry limit
      return retry(callback, nTimes - 1);
    }

    // otherwise, if we hit the retry limit, rethrow the error
    throw reason;
  });
}

// try to save the post up to 5 times
retry(function() {
  return post.save();
}, 5);