獲取TypeScript中的屬性修飾符列表

class Test { 
    @First() 
    @Second() 
    public someAttribute; 
} 

var t = new Test(); 
var decorators = t.getListOfAttributeDecorators("someAttribute"); 
console.log(decorators); // [First, Second]

我想實現「getListOfAttributeDecorators」函數，但不知道如何。或者有沒有其他的方式來獲得屬性裝飾器的列表？獲取TypeScript中的屬性修飾符列表

來源

2016-12-14 mspiderv

你需要維持持有該信息，類似的數據結構：

const REGISTRY = new Map<string, Map<string, string[]>>(); 
function register(cls: string, property: string, decorator: string) { 
    let map: Map<string, string[]>; 

    if (REGISTRY.has(cls)) { 
     map = REGISTRY.get(cls); 
    } else { 
     map = new Map<string, string[]>(); 
     REGISTRY.set(cls, map); 
    } 

    let list: string[]; 
    if (map.has(property)) { 
     list = map.get(property); 
    } else { 
     list = []; 
     map.set(property, list); 
    } 

    if (list.indexOf(decorator) < 0) { 
     list.push(decorator); 
    } 
} 

function First() { 
    return function (cls: any, property: string) { 
     register(cls.constructor.name, property, "First"); 
    } 
} 

function Second() { 
    return function (cls: any, property: string) { 
     register(cls.constructor.name, property, "Second"); 
    } 
} 

class Test { 
    @First() 
    @Second() 
    public someAttribute; 

    public getListOfAttributeDecorators(property: string): string[] { 
     const name = this.constructor.name; 
     return !REGISTRY.has(name) ? [] : REGISTRY.get(name).get(property); 
    } 
} 

let t = new Test(); 
let names = t.getListOfAttributeDecorators("someAttribute"); 
console.log(names); // ["Second", "First"]

（code in playground）

來源

2016-12-14 14:20:02

你能得到關於使用reflect-metadata自定義裝飾數據。通過在裝飾器實現中定義屬性的元數據是可能的 - see on codesandbox。你只能用你卻自定義裝飾第三方庫經常這樣做也用這樣的方式與不同的metadata key

// be sure to import reflect-metadata 
// without importing reflect-metadata Reflect.defineMetadata and other will not be defined. 
import "reflect-metadata"; 

function First(target: Object, propertyKey: string | symbol) { 
    // define metadata with value "First" 
    Reflect.defineMetadata("custom:anotations:first", "First", target, propertyKey); 
} 

function Second(target: Object, propertyKey: string | symbol) { 
    // define metadata with value { second: 2 } 
    // be sure that metadata key is different from First 
    Reflect.defineMetadata("custom:anotations:second", { second: 2 }, target, propertyKey); 
} 

class Test { 
    @First 
    @Second 
    someAttribute: string; 
} 

// get decorators 

function getDecorators(target: any, propertyName: string | symbol): string[] { 
    // get info about keys that used in current property 
    const keys: any[] = Reflect.getMetadataKeys(target, propertyName); 
    const decorators = keys 
    // filter your custom decorators 
    .filter(key => key.toString().startsWith("custom:anotations")) 
    .reduce((values, key) => { 
     // get metadata value. 
     const currValues = Reflect.getMetadata(key, target, propertyName); 
     return values.concat(currValues); 
    }, []); 

    return decorators; 
} 

// test 

var t = new Test(); 
var decorators = getDecorators(t, "someAttribute"); // output is [{ second: 2}, "First"] 
console.log(decorators);

不要忘了，爲了能夠與元數據操作添加"emitDecoratorMetadata": true您tsconfig.json。

獎勵：執行與class decorators支持 - see on codesandox

附：這是一個老問題，但是，我希望我的答案能夠幫助某人。

來源

2018-02-01 21:29:41

獲取TypeScript中的屬性修飾符列表

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