猫鼬方法和静态有什么用?

问题描述：

mongoose 的方法和静态有什么用，它们与普通函数有什么不同?

What is the use of mongoose methods and statics and how are they different from normal functions?

谁能用例子解释一下区别.

Can anyone explain the difference with example.

答

数据库逻辑应该封装在数据模型中.Mongoose 提供了两种方法来做到这一点，方法和静态.方法向文档添加实例方法，而静态向模型本身添加静态类"方法.

Database logic should be encapsulated within the data model. Mongoose provides 2 ways of doing this, methods and statics. Methods adds an instance method to documents whereas Statics adds static "class" methods to the Models itself.

以下面的动物模型为例:

var AnimalSchema = mongoose.Schema({
  name: String,
  type: String,
  hasTail: Boolean
});

module.exports = mongoose.model('Animal', AnimalSchema);

我们可以添加一个方法来查找相似类型的动物，并添加一个静态方法来查找所有有尾巴的动物:

We could add a method to find similar types of animal, and a static method to find all animals with tails:

AnimalSchema.methods.findByType = function (cb) {
  return this.model('Animal').find({ type: this.type }, cb);
};

AnimalSchema.statics.findAnimalsWithATail = function (cb) {
  Animal.find({ hasTail: true }, cb);
};

以下是完整模型，其中包含方法和静态的示例用法:

Here's the full model with example usage for methods and statics:

var AnimalSchema = mongoose.Schema({
  name: String,
  type: String,
  hasTail: Boolean
});

AnimalSchema.methods.findByType = function (cb) {
  return this.model('Animal').find({ type: this.type }, cb);
};

AnimalSchema.statics.findAnimalsWithATail = function (cb) {
  Animal.find({ hasTail: true }, cb);
};

module.exports = mongoose.model('Animal', AnimalSchema);

// example usage:

var dog = new Animal({
  name: 'Snoopy',
  type: 'dog',
  hasTail: true
});

dog.findByType(function (err, dogs) {
  console.log(dogs);
});

Animal.findAnimalsWithATail(function (animals) {
  console.log(animals);
});

猫鼬方法和静态有什么用?

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