Angular8 简单表单验证的实现示例

<form nz-form [nzlayout]="'inline'" [formgroup]="validateform" (ngsubmit)="submitform()">
 <nz-form-item>
  <nz-form-control nzerrortip="please input your username!">
   <nz-input-group nzprefixicon="user">
    <input formcontrolname="username" nz-input placeholder="username" />
   </nz-input-group>
  </nz-form-control>
 </nz-form-item>
 <nz-form-item>
  <nz-form-control nzerrortip="please input your password!">
   <nz-input-group nzprefixicon="lock">
    <input formcontrolname="password" nz-input type="password" placeholder="password" />
   </nz-input-group>
  </nz-form-control>
 </nz-form-item>
 <nz-form-item>
  <nz-form-control>
   <button nz-button nztype="primary" [disabled]="!validateform.valid">log in</button>
  </nz-form-control>
 </nz-form-item>
</form>

validateform!: formgroup;

 submitform(): void {
  for (const i in this.validateform.controls) {
   this.validateform.controls[i].markasdirty();
   this.validateform.controls[i].updatevalueandvalidity();
  }
 }

 constructor(private fb: formbuilder) {}

 ngoninit(): void {
  this.validateform = this.fb.group({
   username: [null, [validators.required]],
   password: [null, [validators.required]],
   remember: [true]
  });
 }

<nz-form-control [nzerrortip]="geterrtipbyfield('username')">
   <nz-input-group nzprefixicon="user">
    <input formcontrolname="username" nz-input placeholder="username" />
   </nz-input-group>
  </nz-form-control>

export class simpleformcomponent implements oninit {
 validateform: formgroup;
 errmessagemap = {};

 constructor(
  private fb: formbuilder
 ) { }

 ngoninit() {
  this.errmessagemap = {
   username: {
    required: 'please input your name!',
    minlength: 'please input at least least 5 character'
   },
   password: {
    required: 'please input your password!'
   }
  };
  this.validateform = this.fb.group({
   username: [null, [validators.required, validators.minlength(5)]],
   password: [null, [validators.required]],
   remember: [true]
  }, { updateon: 'change' });
 }
 submitform(): void {
  if (this.validateform.controls) {
   for (const i in this.validateform.controls) {
    if (this.validateform.controls[i]) {
     this.validateform.controls[i].markasdirty();
     this.validateform.controls[i].updatevalueandvalidity();
    }
   }
  }
 }
 geterrtipbyfield(fieldname) {
  const errors = this.validateform.get(fieldname).errors;
  let errmsg = '';
  for (const key in errors) {
   if (errors.hasownproperty(key)) {
    errmsg += this.errmessagemap[fieldname][key];
   }
  }
  return errmsg;
 }

}