Johnny Wang Blog

Parse Javascript 文檔閱讀筆記

這是一系列閱讀 Parse Javascript, Parse Cloud, Parse Server 的一系列學習筆記，作為學習的紀錄與複習使用，也歡迎有興趣的朋友們看看摟，內容並不會包含所有文檔，主要都是我自己閱讀後認為最重要且必須的部分，剩下的文檔可以實際用到時再深入研究與探索

$ npm install parse

Objects

Querys

以下 key 表示 object field name

Query methods(常用部分)

  • get(objectId): Promise
  • first(): Promise
  • find(): Promise
  • count(): Promise
  • aggregate(pipeline): Promise
  • distinct(key): Promise

Constraints(常用部分)

compare 比較

  • equalTo(key, value)
  • notEqualTo(key, value)
  • greaterThan(key, number)
  • greaterThanOrEqualTo(key, number)
  • lessThan(key, number)
  • lessThanOrEqualTo(key, number)
  • matches(key, RegExp)

count 數量

  • limit(number)
  • skip([number]): 常用來製作 pagination
  • withCount(): query 物件時一併計算總數返回 count，較耗效能，不受 limit 數量限制，常用來製作 pagination，如不需返回物件內容僅需要取得數量，推薦使用 query count 方法

sort 排序

  • ascending(key)
  • descending(key)

list 清單

  • containedIn(key, value[])
  • notContainedIn(key, value[])

exist 存在值

  • exists(key)
  • doesNotExist(key)

選取排除欄位

  • select(key1, key2, ...keys[])
  • exclude(key1, key2, ...keys[])
  • include(key or [key1, key2])

比對 query keys

  • matchesKeyInQuery(): TODO
  • doesNotMatchKeyInQuery()
  • matchesQuery(key, keyQuery)
  • doesNotMatchQuery(key, keyQuery)
// 範例：取得未擁有 profile 關聯的 users
const queryUser = new Parse.Query(Parse.User);
const queryProfile = new Parse.Query('Profile');
queryUser.doesNotMatchKeyInQuery('objectId', 'owner.objectId', queryProfile);
const res = await queryUser.explain().find({ useMasterKey: true });
console.log(res);

Relations

Error Handling

const query = new Parse.Query(Note);
query.get("aBcDeFgH").then((results) => {
  // 這裡不會執行
  alert("Everything went fine!");
}, (error) => {
  // 這裡會執行
  // error 是一個帶著錯誤資訊的 Parse.Error 實例
  if (error.code === Parse.Error.OBJECT_NOT_FOUND) {
    alert("Uh oh, we couldn't find the object!");
  } else if (error.code === Parse.Error.CONNECTION_FAILED) {
    alert("Uh oh, we couldn't even connect to the Parse Cloud!");
  }
});

// or using catch
query.get("aBcDeFgH").then((results) => {
  // ...
}).catch((error) => {
  // ...
});

如果像是 save, signUp 這種針對特定 object 處理的方法，在 error 函數的第一個參數將會是 object，第二個才是 error object

詳細錯誤清單請在Error Codes 這裡查詢open in new window

Security

Parse options

Class Level Permission

Memo

Subclass

const Monster = Parse.Object.extend("Monster", {
  // Instance methods
  hasSuperHumanStrength: function () {
    return this.get("strength") > 18;
  },
  // Instance properties go in an initialize method
  initialize: function (attrs, options) {
    this.sound = "Rawr"
  }
}, {
  // Class methods
  spawn: function(strength) {
    const monster = new Monster();
    monster.set("strength", strength);
    return monster;
  }
});

const monster = Monster.spawn(200);
alert(monster.get('strength'));  // Displays 200.
alert(monster.sound); // Displays Rawr.

透過 Parse.Object.extend 製作的 Subclass 可以直接調用相關方法，返回的 instance 也會自動套用延伸功能。

v1.6.0 後也可透過 ES6 Class 對 Parse.Object 進行 extends 創建 Subclass，但必須在註冊後透過 registerSubclass 才能在 query 後返回繼續使用 Subclass 中的屬性、方法。

class MyMonster extends Parse.Object {
  constructor() {
    // 繼承原 Monster Class
    super('Monster');
    // All other initialization
    this.sound = 'Rawr';
  }

  hasSuperHumanStrength() {
    return this.get('strength') > 18;
  }

  static spawn(strength) {
    const monster = new MyMonster();
    monster.set('strength', strength);
    return monster;
  }
}

// 對原 Monster 註冊其 Subclass "MyMonster"
Parse.Object.registerSubclass('Monster', MyMonster);

Query on Array

query.equalTo("arrayKey", 2);

Query on String

query.startsWith("someKey", "match value");
query.fullText("someKey", "match fullText"); // case insensitive

Query with RegExp

const numbers = [1234, 4321];
query.matches('someKey', new RegExp(`(${numbers.join('|')})$`)); // will match ~34, ~21

Relational Queries

  • matchesQuery 取得所有含有 image 的 Post 物件中的 Comments
const Post = Parse.Object.extend("Post");
const Comment = Parse.Object.extend("Comment");
const innerQuery = new Parse.Query(Post);
innerQuery.exists("image");
const query = new Parse.Query(Comment);
query.matchesQuery("post", innerQuery);
// comments now contains the comments for posts with images.
const comments = await query.find();
  • objectId equalTo by relational query
const post = new Post();
post.id = "1zEcyElZ80";
query.equalTo("post", post);
  • include to join in other Object
const query = new Parse.Query(Comment);

// Retrieve the most recent ones
query.descending("createdAt");

// Only retrieve the last ten
query.limit(10);

// Include the post data with each comment
query.include("post");

Compound Query

  • or
const lotsOfWins = new Parse.Query("Player");
lotsOfWins.greaterThan("wins", 150);

const fewWins = new Parse.Query("Player");
fewWins.lessThan("wins", 5);

const mainQuery = Parse.Query.or(lotsOfWins, fewWins);
  • complex and(query itself will act as basic and)
const age16Query = new Parse.Query("User");
age16Query.equalTo("age", 16);

const age18Query = new Parse.Query("User");
age18Query.equalTo("age", 18);

const friends0Query = new Parse.Query("User");
friends0Query.equalTo("friends", 0);

const friends2Query = new Parse.Query("User");
friends2Query.greaterThan("friends", 2);

const mainQuery = Parse.Query.and(
  Parse.Query.or(age16Query, age18Query),
  Parse.Query.or(friends0Query, friends2Query)
);

Aggregate

  • group pipeline Grouping by name field, $ before field name will tell Parse Server its a field name
const pipeline = [
  { group: { objectId: '$score' } }
];
const query = new Parse.Query("User");
const res = await query.aggregate(pipeline)
console.log(res)
  • project pipeline(keys, select)
const pipeline = [
  { project: { name: 1 } }
];
  • match pipeline(equalTo)
const pipeline = [
  { match: { name: 'BBQ' } }
];

Passing context on save

object.save(null, { context: { myArg: true } });

Parse.Cloud.beforeSave('MyClass', req => {
  let myArg = req.context.myArg;
});
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Contributors: johnnywang