这是我到目前为止使用的：

import { ValidatorFn,AsyncValidatorFn,Validators as V,FormControl } from '@angular/forms';

// the need in this validators is the non-trimming angular standard behavior
// see https://github.com/angular/angular/issues/8503
export class Validators {

  public static required(control: FormControl) {
    if (!control.value || typeof control.value === 'string' && !control.value.trim()) {
      return {
        required: true
      };
    }

    return null;
  }

  public static minLength(length: number): ValidatorFn {
    return (control: FormControl) => {
      if (!control.value || typeof control.value === 'string' && control.value.trim().length < length) {
        return {
          minlength: true
        };
      }

      return null;
    };
  }

  public static maxLength(length: number): ValidatorFn {
    return (control: FormControl) => {
      if (control.value && typeof control.value === 'string' && control.value.trim().length > length) {
        return {
          maxlength: true
        };
      }

      return null;
    };
  }

  public static pattern(pattern: string): ValidatorFn {
    return V.pattern(pattern);
  }

  public static minAmount(amount: number): ValidatorFn {
    return (control: FormControl) => {
      if (control.value && control.value.length < amount) {
        return {
          minamount: true
        };
      }

      return null;
    };
  }

  public static maxAmount(amount: number): ValidatorFn {
    return (control: FormControl) => {
      if (control.value && control.value.length > amount) {
        return {
          maxamount: true
        };
      }

      return null;
    };
  }

  public static compose(validators: ValidatorFn[]): ValidatorFn {
    return V.compose(validators);
  }

  public static composeAsync(validators: AsyncValidatorFn[]): AsyncValidatorFn {
    return V.composeAsync(validators);
  }

};

这模仿了字符串输入的标准maxLength,minLength和必需的验证,但是修剪和代理标准的其他功能.

要使用它,只需导入验证器而不是@ angular / forms one,例如：

import { FormControl } from '@angular/forms';
import { Validators } from 'path/to/validators';

...
let control = new FormControl('',Validators.compose(
  Validators.required,Validators.minLength(6)
));
...

这可能不会修剪模型,但它解决了请求中指定的验证问题.