文章索引

npm地址：https://www.npmjs.com/package/reflect-metadata

一、安装

npm install reflect-metadata

1	npm install reflect-metadata

二、背景

装饰器通过声明式语法在定义类时添加增强类及其成员的能力；
示踪器将注释附加到类的静态属性上；
诸如C＃（.NET）和Java之类的语言支持将元数据添加到类型的属性或注释，以及用于读取元数据的反射API。

三、目标

许多用例（组合/依赖注入，运行时类型断言，反射/镜像，测试）都希望能够以一致的方式向类中添加其他元数据；
为了使各种工具和库能够推理出元数据，需要一种一致的方法；
产生元数据的修饰器（nee。“ Annotations”）通常需要与可变修饰器组合在一起；
元数据不仅可以用在对象上，也可以通过相关捕获器用在Proxy上；
对开发人员来说，定义新的元数据生成装饰器应该简洁易用；
元数据应该与ECMAScript的其他语言和运行效果一致；

四、语法

运行命令行：tsc index.ts –target ES5 -w –experimentalDecorators –emitDecoratorMetadata

import 'reflect-metadata'

/**
 * Declarative definition of metadata
 * 元数据的声明式定义
 * class C {
 *    @Reflect.metadata(metadataKey, metadataValue)
 *    method() {}
 * }
 */
class C1 {
  @Reflect.metadata('key1', 'value1')
  name: string = 'hello'

  @Reflect.metadata('key2', 'value2')
  method() {}
}

const value1 = Reflect.getMetadata('key1', new C1(), 'name')
const value2 = Reflect.getMetadata('key2', new C1(), 'method')
console.log('Syntax.1', value1, value2) // value1 value2


/**
 * Imperative definition of metadata
 * 元数据的命令式定义
 * Reflect.defineMetadata(metadataKey, metadataValue, C.prototype, 'method')
 */
Reflect.defineMetadata('key3', 'value3', C1.prototype, 'name')

const value3 = Reflect.getMetadata('key3', C1.prototype, 'name')
console.log('Syntax.2', value3) // value3

/**
 * Imperative introspection of metadata
 * 元数据的命令自省
 * let obj = new C()
 * let metadataValue = Reflect.getMetadata(metadataKey, obj, 'method')
 */
class A {
  @Reflect.metadata('A-key1', 'A-value1')
  method() {}
}
let obj = new A()
let AMetadataValue1 = Reflect.getMetadata('A-key1', obj, 'method')
console.log('AMetadataValue1', AMetadataValue1)

import 'reflect-metadata'

/**

* Declarative definition of metadata

* 元数据的声明式定义

* class C {

* @Reflect.metadata(metadataKey, metadataValue)

* method() {}

* }

class C1 {

@Reflect.metadata('key1', 'value1')

@Reflect.metadata('key2', 'value2')

method() {}

}

const value1 = Reflect.getMetadata('key1', new C1(), 'name')

const value2 = Reflect.getMetadata('key2', new C1(), 'method')

console.log('Syntax.1', value1, value2) // value1 value2

/**

* Imperative definition of metadata

* 元数据的命令式定义

* Reflect.defineMetadata(metadataKey, metadataValue, C.prototype, 'method')

Reflect.defineMetadata('key3', 'value3', C1.prototype, 'name')

const value3 = Reflect.getMetadata('key3', C1.prototype, 'name')

console.log('Syntax.2', value3) // value3

/**

* Imperative introspection of metadata

* 元数据的命令自省

* let obj = new C()

* let metadataValue = Reflect.getMetadata(metadataKey, obj, 'method')

class A {

@Reflect.metadata('A-key1', 'A-value1')

method() {}

}

let obj = new A()

let AMetadataValue1 = Reflect.getMetadata('A-key1', obj, 'method')

console.log('AMetadataValue1', AMetadataValue1)

五、API

/**
 * define metadata on an object or property
 * 在对象或属性上定义元数据
 * Reflect.defineMetadata(metadataKey, metadataValue, target)
 * Reflect.defineMetadata(metadataKey, metadataValue, target, propertyKey)
 */
class A1 {
  method() {}
}
Reflect.defineMetadata('A1-key1', 'A1-value1', A1)
Reflect.defineMetadata('A1-key2', 'A1-value2', A1, 'method')

let A1Result1 = Reflect.getMetadata('A1-key1', A1)
let A1Result2 = Reflect.getMetadata('A1-key2', A1, 'method')
console.log('A1Result1', A1Result1)
console.log('A1Result2', A1Result2)

/**
 * check for presence of a metadata key on the prototype chain of an object or property
 * 检查对象或属性的原型链上是否存在元数据键
 * let result = Reflect.hasMetadata(metadataKey, target)
 * let result = Reflect.hasMetadata(metadataKey, target, propertyKey)
 */
@Reflect.metadata('c2-key1', 'c2-value1')
class C2 {
  @Reflect.metadata('c2-key2', 'c2-value2')
  name: string = 'bob'
}

let c2Result1 = Reflect.hasMetadata('c2-key1', C2) // true
let c2Result2 = Reflect.hasMetadata('c2-key2', C2.prototype, 'name') // true
let c2Result3 = Reflect.hasMetadata('c2-key3', C2.prototype, 'name') // false
console.log('hasMetadata', c2Result1, c2Result2, c2Result3)

class C21 extends C2 {
  method() {}
}
let c2Result4 = Reflect.hasMetadata('c2-key1', C21) // true
let c2Result5 = Reflect.hasMetadata('c2-key2', C21.prototype, 'name') // true
console.log('hasMetadata', c2Result4, c2Result5)

/**
 * check for presence of an own metadata key of an object or property
 * 检查对象或属性是否存在自己的元数据键值
 * let result = Reflect.hasOwnMetadata(metadataKey, target)
 * let result = Reflect.hasOwnmetadata(metadataKey, target, propertyKey)
 */
function age(age: number) {
  console.log('age')
  return function (target: any, propertyKey: string) {
    Reflect.defineMetadata('c3-key3', age, target, propertyKey)
  }
}

@Reflect.metadata('c3-key1', 'c3-value1')
class C3 {
  @Reflect.metadata('c3-key2', 'c3-key2')
  name: string = 'bob'

  @age(18)
  age: number = 18
}

let c3Result1 = Reflect.hasOwnMetadata('c3-key1', C3) // true
let c3Result2 = Reflect.hasOwnMetadata('c3-key2', C3.prototype, 'name') // true
let c3Result3 = Reflect.hasOwnMetadata('c3-key3', C3.prototype, 'age') // true
let c3Result4 = Reflect.hasOwnMetadata('c3-key3', new C3(), 'age') // false
console.log('hasOwnMetadata', c3Result1, c3Result2, c3Result3, c3Result4)

class C31 extends C3 {
  method() {}
}

let c3Result5 = Reflect.hasOwnMetadata('c3-key1', C31) // false
let c3Result6 = Reflect.hasOwnMetadata('c3-key2', C31, 'name') // false

console.log('hasOwnMetadata', c3Result5, c3Result6)

/**
 * get metadata value of a metadata key on the prototype chain of an object or property
 * 在对象或属性的原型链上获取元数据键的元数据值
 * let result = Reflect.getMetadata(metadataKey, target)
 * let result = Reflect.getMetadata(metadataKey, target, propertyKey)
 */

/**
 * get metadata value of an own metadata key of an object or property
 * 获取对象或属性自己的元数据键的元数据值
 * let result = Reflect.getOwnMetadata(metadataKey, target)
 * let result = Reflect.getOwnMetadata(metadataKey, target, propertyKey)
 */

/**
 * get all metadata keys on the prototype chain of an object or property
 * 获取对象或属性上所有原型链上的元数据键值
 * let result = Reflect.getMetadataKeys(target)
 * let result = Reflect.getMetadataKeys(target, propertyKey)
 */
@Reflect.metadata('c4-key2', 'c4-value2')
class C4 {
  @Reflect.metadata('c4-key3', 'c4-value3')
  name: string = 'bob'

  @Reflect.metadata('c4-key1', 'c4-value1')
  method() {
    return 'hello'
  }
}

let c4Result1 = Reflect.getMetadataKeys(new C4(), 'method')
let c4Result2 = Reflect.getMetadataKeys(C4)
let c4Result3 = Reflect.getMetadataKeys(new C4(), 'name')
let c4Result4 = Reflect.getMetadataKeys(C4.prototype, 'method')
console.log('c4Result1', c4Result1) // [ 'design:returntype', 'design:paramtypes', 'design:type', 'c4-key1' ]
console.log('c4Result2', c4Result2) // [ 'c4-key2' ]
console.log('c4Result3', c4Result3) // [ 'design:type', 'c4-key3' ]
console.log('c4Result4', c4Result4) // [ 'design:returntype', 'design:paramtypes', 'design:type', 'c4-key1' ]

class C41 extends C4 {}
let c41Result1 = Reflect.getMetadataKeys(C41)
let c41Result2 = Reflect.getMetadataKeys(C41.prototype, 'method')
console.log('C41Result1', c41Result1) // [ 'c4-key2' ]
console.log('c41Result2', c41Result2) // [ 'design:returntype', 'design:paramtypes', 'design:type', 'c4-key1' ]

/**
 * get all own metadata keys of an object or property
 * 获取对象或属性的所有自有元数据键
 * let result = Reflect.getOwnMetadataKeys(target)
 * let result = Reflect.getOwnMetadataKeys(target, propertyKey)
 */
@Reflect.metadata('c5-key2', 'value2')
class C5 {
  @Reflect.metadata('c5-key4', 'value4')
  name: string = 'bob'

  @Reflect.metadata('c5-key1', 'value1')
  method() {
    return 'hello'
  }
}
let c5Result1 = Reflect.getOwnMetadataKeys(C5.prototype, 'method')
let c5Result2 = Reflect.getOwnMetadataKeys(new C5(), 'method')
let c5Result3 = Reflect.getOwnMetadataKeys(C5)
let c5Result4 = Reflect.getOwnMetadataKeys(C5.prototype, 'name')
let c5Result5 = Reflect.getOwnMetadataKeys(new C5(), 'name')

console.log('c5Result1', c5Result1) // [ 'design:returntype', 'design:paramtypes', 'design:type', 'c5-key1' ]
console.log('c5Result2', c5Result2) // []
console.log('c5Result3', c5Result3) // [ 'c5-key2' ]
console.log('c5Result4', c5Result4) // [ 'design:type', 'c5-key4' ]
console.log('c5Result5', c5Result5) // []

class C51 extends C5 {}

let c51Result1 = Reflect.getOwnMetadataKeys(C51)
console.log('c51Result1', c51Result1) // []

/**
 * delete metadata from an object or property
 * 从对象或属性上删除元数据
 * let result = Reflect.deleteMetadata(metadataKey, target)
 * let result = Reflect.deleteMetadata(metadataKey, target, propertyKey)
 */

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/**

* define metadata on an object or property

* 在对象或属性上定义元数据

* Reflect.defineMetadata(metadataKey, metadataValue, target)

* Reflect.defineMetadata(metadataKey, metadataValue, target, propertyKey)

class A1 {

method() {}

}

Reflect.defineMetadata('A1-key1', 'A1-value1', A1)

Reflect.defineMetadata('A1-key2', 'A1-value2', A1, 'method')

let A1Result1 = Reflect.getMetadata('A1-key1', A1)

let A1Result2 = Reflect.getMetadata('A1-key2', A1, 'method')

console.log('A1Result1', A1Result1)

console.log('A1Result2', A1Result2)

/**

* check for presence of a metadata key on the prototype chain of an object or property

* 检查对象或属性的原型链上是否存在元数据键

* let result = Reflect.hasMetadata(metadataKey, target)

* let result = Reflect.hasMetadata(metadataKey, target, propertyKey)

@Reflect.metadata('c2-key1', 'c2-value1')

class C2 {

@Reflect.metadata('c2-key2', 'c2-value2')

}

let c2Result1 = Reflect.hasMetadata('c2-key1', C2) // true

let c2Result2 = Reflect.hasMetadata('c2-key2', C2.prototype, 'name') // true

let c2Result3 = Reflect.hasMetadata('c2-key3', C2.prototype, 'name') // false

console.log('hasMetadata', c2Result1, c2Result2, c2Result3)

class C21 extends C2 {

method() {}

}

let c2Result4 = Reflect.hasMetadata('c2-key1', C21) // true

let c2Result5 = Reflect.hasMetadata('c2-key2', C21.prototype, 'name') // true

console.log('hasMetadata', c2Result4, c2Result5)

/**

* check for presence of an own metadata key of an object or property

* 检查对象或属性是否存在自己的元数据键值

* let result = Reflect.hasOwnMetadata(metadataKey, target)

* let result = Reflect.hasOwnmetadata(metadataKey, target, propertyKey)

function age(age: number) {

console.log('age')

return function (target: any, propertyKey: string) {

Reflect.defineMetadata('c3-key3', age, target, propertyKey)

}

@Reflect.metadata('c3-key1', 'c3-value1')

class C3 {

@Reflect.metadata('c3-key2', 'c3-key2')

@age(18)

age: number = 18

}

let c3Result1 = Reflect.hasOwnMetadata('c3-key1', C3) // true

let c3Result2 = Reflect.hasOwnMetadata('c3-key2', C3.prototype, 'name') // true

let c3Result3 = Reflect.hasOwnMetadata('c3-key3', C3.prototype, 'age') // true

let c3Result4 = Reflect.hasOwnMetadata('c3-key3', new C3(), 'age') // false

console.log('hasOwnMetadata', c3Result1, c3Result2, c3Result3, c3Result4)

class C31 extends C3 {

method() {}

}

let c3Result5 = Reflect.hasOwnMetadata('c3-key1', C31) // false

let c3Result6 = Reflect.hasOwnMetadata('c3-key2', C31, 'name') // false

console.log('hasOwnMetadata', c3Result5, c3Result6)

/**

* get metadata value of a metadata key on the prototype chain of an object or property

* 在对象或属性的原型链上获取元数据键的元数据值

* let result = Reflect.getMetadata(metadataKey, target)

* let result = Reflect.getMetadata(metadataKey, target, propertyKey)

/**

* get metadata value of an own metadata key of an object or property

* 获取对象或属性自己的元数据键的元数据值

* let result = Reflect.getOwnMetadata(metadataKey, target)

* let result = Reflect.getOwnMetadata(metadataKey, target, propertyKey)

/**

* get all metadata keys on the prototype chain of an object or property

* 获取对象或属性上所有原型链上的元数据键值

* let result = Reflect.getMetadataKeys(target)

* let result = Reflect.getMetadataKeys(target, propertyKey)

@Reflect.metadata('c4-key2', 'c4-value2')

class C4 {

@Reflect.metadata('c4-key3', 'c4-value3')

@Reflect.metadata('c4-key1', 'c4-value1')

method() {

return 'hello'

}

let c4Result1 = Reflect.getMetadataKeys(new C4(), 'method')

let c4Result2 = Reflect.getMetadataKeys(C4)

let c4Result3 = Reflect.getMetadataKeys(new C4(), 'name')

let c4Result4 = Reflect.getMetadataKeys(C4.prototype, 'method')

console.log('c4Result1', c4Result1) // [ 'design:returntype', 'design:paramtypes', 'design:type', 'c4-key1' ]

console.log('c4Result2', c4Result2) // [ 'c4-key2' ]

console.log('c4Result3', c4Result3) // [ 'design:type', 'c4-key3' ]

console.log('c4Result4', c4Result4) // [ 'design:returntype', 'design:paramtypes', 'design:type', 'c4-key1' ]

class C41 extends C4 {}

let c41Result1 = Reflect.getMetadataKeys(C41)

let c41Result2 = Reflect.getMetadataKeys(C41.prototype, 'method')

console.log('C41Result1', c41Result1) // [ 'c4-key2' ]

console.log('c41Result2', c41Result2) // [ 'design:returntype', 'design:paramtypes', 'design:type', 'c4-key1' ]

/**

* get all own metadata keys of an object or property

* 获取对象或属性的所有自有元数据键

* let result = Reflect.getOwnMetadataKeys(target)

* let result = Reflect.getOwnMetadataKeys(target, propertyKey)

@Reflect.metadata('c5-key2', 'value2')

class C5 {

@Reflect.metadata('c5-key4', 'value4')

@Reflect.metadata('c5-key1', 'value1')

method() {

return 'hello'

}

let c5Result1 = Reflect.getOwnMetadataKeys(C5.prototype, 'method')

let c5Result2 = Reflect.getOwnMetadataKeys(new C5(), 'method')

let c5Result3 = Reflect.getOwnMetadataKeys(C5)

let c5Result4 = Reflect.getOwnMetadataKeys(C5.prototype, 'name')

let c5Result5 = Reflect.getOwnMetadataKeys(new C5(), 'name')

console.log('c5Result1', c5Result1) // [ 'design:returntype', 'design:paramtypes', 'design:type', 'c5-key1' ]

console.log('c5Result2', c5Result2) // []

console.log('c5Result3', c5Result3) // [ 'c5-key2' ]

console.log('c5Result4', c5Result4) // [ 'design:type', 'c5-key4' ]

console.log('c5Result5', c5Result5) // []

class C51 extends C5 {}

let c51Result1 = Reflect.getOwnMetadataKeys(C51)

console.log('c51Result1', c51Result1) // []

/**

* delete metadata from an object or property

* 从对象或属性上删除元数据

* let result = Reflect.deleteMetadata(metadataKey, target)

* let result = Reflect.deleteMetadata(metadataKey, target, propertyKey)

北鱼IT

typescript 库：reflect-metadata使用

一、安装

二、背景

三、目标

四、语法

五、API