[英]Promises in Sequelize: how to get results from each promise
在Sequelize> = 1.7中, 我們可以使用promises
你能解釋一下我如何從這個代碼中獲得每個用戶的值:
var User = sequelize.define("user", {
username: Sequelize.STRING
})
User
.sync({ force: true })
.then(function() { return User.create({ username: 'John' }) })
.then(function(john) { return User.create({ username: 'Jane' }) })
.then(function(jane) { return User.create({ username: 'Pete' }) })
.then(function(pete) {
console.log("we just created 3 users :)")
console.log("this is pete:")
console.log(pete.values)
// what i want:
console.log("this is jane:")
console.log(jane.values)
console.log("this is john:")
console.log(john.values)
})
UPD
所有值都需要與其他模型設置關聯。 其實我需要一些像這樣的代碼:
User.hasMany(Group)
Group.hasMany(User)
User
.sync({ force: true })
.then(function() { return User.create({ username: 'John' }) })
.then(function(john) { return User.create({ username: 'Jane' }) })
.then(function(jane) { return User.create({ username: 'Pete' }) })
.then(function(pete) { return Group.findOrCreate({id: 1}) })
.then(function(group) {return group.setUsers([john, jane, pete])})
.then(function(result) { console.log(result)})
})
Bluebird方式是集合輔助函數 。
如果要並行創建它們,請使用map
:
User.sync({ force: true })
.then(function() {
return Promise.map( ['John', 'Jane', 'Pete'], function(name) {
return User.create({ username: name });
})
}).spread(function(john, jane, pete) {
console.log("we just created 3 users :)")
console.log("this is john:")
console.log(john.values)
console.log("this is jane:")
console.log(jane.values)
console.log("this is pete:")
console.log(pete.values)
})
如果您需要連續創建它們,只需將其更改為mapSeries
(3.0+)。
如果數組不需要是動態的,並且您只想通過承諾鏈傳遞共享值(如示例中所示),請查看如何在.then()鏈中訪問先前的承諾結果? 。
不使用其他庫(如果需要維護創建的順序),可以通過在包含范圍內創建包含值的變量來實現:
var created = {};
User
.sync({ force: true })
.then(function() { return User.create({ username: 'John' }) })
.then(function(john) { created.john = john; return User.create({ username: 'Jane' }) })
.then(function(jane) { created.jane = jane; return User.create({ username: 'Pete' }) })
.then(function(pete) {
created.pete = pete;
console.log("we just created 3 users :)")
console.log("this is pete:")
console.log(created.pete.values)
// what i want:
console.log("this is jane:")
console.log(created.jane.values)
console.log("this is john:")
console.log(created.john.values)
})
一般來說,我建議你傾向於@ Bergi的答案,它會創建一個Promise列表並等待所有的承諾完成。
根據問題更新進行編輯:
使用更新后的代碼塊,建設上@的BERGI的建議Promise.map
,可避免與類似下面的一個更高的范圍使用變量:
User.hasMany(Group)
Group.hasMany(User)
User
.sync({ force: true })
.then(function() {
var users = Promise.map( ['John', 'Jane', 'Pete'], function(name) {
return User.create({ username: name });
});
var group = Group.findOrCreate({id: 1});
return Promise.all([group, users]);
})
.spread(function(group, users) {return group.setUsers(users)})
.then(function(result) { console.log(result)})
})
試試這個...
User
.sync({ force: true })
.then(function () {
return User.create({ username: 'John' });
})
.then(function (john) {
console.log("this is john:");
console.log(john.values);
return User.create({ username: 'Jane' });
})
.then(function (jane) {
console.log("this is jane:");
console.log(jane.values);
return User.create({ username: 'Pete' });
})
.then(function (pete) {
console.log("we just created 3 users :)");
console.log("this is pete:");
console.log(pete.values);
});
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