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Typescript decorators+反射元数据

reflect-metadata typescript

0

nomadoda · 技术社区 · 6 年前

我用的是一个房产装饰师 Field 把它的“钥匙”推到 fields

export function Field(): PropertyDecoratorÂ {
    return (target, key) => {
        const fields = Reflect.getMetadata('fields', target) ||Â [];
        if (!fields.includes(key)) {
            fields.push(key)
        }
        Reflect.defineMetadata('fields', fields, target)
    }
}

然后我有一个抽象基类 Form

abstract class Form {
    get fields() {
        return Reflect.getMetadata('fields', this) ||Â [];
    }
}

到目前为止,我已经能够成功地使用它来区分表单字段和其他类属性。考虑这些类:

abstract class UserForm extends Form {
    @Field()
    public firstName: string

    @Field()
    public lastName: string

    get fullName() {
        return this.firstName + ' ' + this.lastName;
    }
}

class AdminForm extends UserForm {
    @Field()
    roles: string[]
}

const form = new AdminForm()
console.log(form.fields)
// ['roles', 'firstName', 'lastName']

当我定义一个姐妹类 AdminForm MemberForm . 当存在多个子类时 形式 getter返回所有字段:

class MemberForm extends UserForm {
    @Field()
    memberSince: Date;
}

const form = new AdminForm()
console.log(form.fields)
// ['roles', 'firstName', 'lastName', 'memberSince'] <--!!!

这对我来说毫无意义。为什么 memberSince 字段出现在的实例上 ? 如何在不同的子类上定义不同的字段?

0 回复 | 直到 6 年前

1

2

Titian Cernicova-Dragomir 6 年前

问题是 getMetadata getOwnMetadata 若要仅在添加新字段时获取当前类的数组字段,并且在获取字段时,需要遍历属性链以获取所有基类字段。

import 'reflect-metadata'
export function Field(): PropertyDecorator {
  return (target, key) => {
      const fields = Reflect.getOwnMetadata('fields', target) || [];
      if (!fields.includes(key)) {
          fields.push(key)
      }
      Reflect.defineMetadata('fields', fields, target)
  }
}

abstract class Form {
  get fields() {
      let fields = []
      let target = Object.getPrototypeOf(this);
      while(target != Object.prototype) {
        let childFields = Reflect.getOwnMetadata('fields', target) || [];
        fields.push(...childFields);
        target = Object.getPrototypeOf(target);
      }
      return fields;
  }
}

abstract class UserForm extends Form {
  @Field()
  public firstName!: string

  @Field()
  public lastName!: string

  get fullName() {
      return this.firstName + ' ' + this.lastName;
  }
}

class AdminForm extends UserForm {
  @Field()
  roles!: string[]
}

const form1 = new AdminForm()
console.log(form1.fields) // ['roles', 'firstName', 'lastName']

class MemberForm extends UserForm {
  @Field()
  memberSince!: Date;
}

const form2 = new MemberForm()
console.log(form2.fields) // ["memberSince", "firstName", "lastName"]