Angular动态组件&响应式表单的实现[附源码]

本文将通过一个简单的例子简单展示Angular动态组件+响应式表单的使用。
【关键字】： Angular，动态组件，响应式表单，ComponentFactoryResolver，ViewContainerRef，ReactiveFormsModule
最终代码在最后

• 新建一个项目

ng new dynamic-form

• 新建一个模块（并在app.module中导入DynamicFormModule）

import { CommonModule } from '@angular/common';
import { NgModule } from '@angular/core';
import { ReactiveFormsModule } from '@angular/forms';

@NgModule({
    declarations: [  ],
    imports: [
        CommonModule,
        ReactiveFormsModule,
    ],
    entryComponents: [    ],
    exports: [    ]
})
export class DynamicFormModule { }

• 现在，我们需要创建用于创建动态表单的容器
  动态表单的入口点是主容器。这将是我们的动态表单模块公开的唯一组件，负责接受表单配置并创建表单。

// dynamic-form-module components/dyanmic-form.component 
import { Component, EventEmitter, Input, OnInit, Output } from '@angular/core';
import { FormBuilder, FormGroup, Validators } from '@angular/forms';
import { FromItemConfig } from '../../models/dynamic-form.model';

@Component({
    selector: 'app-dynamic-form',
    templateUrl: './dynamic-form.component.html',
    styleUrls: ['./dynamic-form.component.scss']
})
export class DynamicFormComponent implements OnInit {
    @Input()
    public formConfigs: Array = new Array();
   
    @Output()
    public readonly submitted: EventEmitter = new EventEmitter();

    public formGroup: FormGroup;
    public constructor(private fb: FormBuilder ) {
this.formGroup = this.fb.group({});
    }

    public ngOnInit(): void {
        this.setFromControl();
    }

    public submitHandler(): void {
        // tslint:disable-next-line: forin
        for (const i in this.formGroup.controls) {
            this.formGroup.controls[i].markAsDirty();
            this.formGroup.controls[i].updateValueAndValidity();
        }
        if (this.formGroup.valid) {
            this.submitted.emit(this.formGroup.value);
        }
    }

    private setFromControl(): void {
        this.formConfigs?.forEach((control, idx) => {
            this.formGroup.addControl(control.controlName,
                this.fb.control(control.defaultValue || null, control?.required ? Validators.required : null));
        });
    }
}

由于我们的表单是动态表单，因此我们需要接受一个配置数组才能知道要创建什么。为此，我们正在使用，@Input()它接受任何对象数组。
对于配置中的每个项目，我们都希望该对象包含一些必要属性，所以我们顶一个一个接口FromItemConfig

export interface FromItemConfig {
    type: FromItemType;
    controlName: string;
    label: string;
    defaultValue?: T;
    disabled?: boolean;
    required?: boolean;
    options?: Array;
}
export interface OptionItem {
    value: any;
    label: string;
}
// 这里根据我们已经支持的表单控件类型定义了一个枚举
export enum FromItemType {
    'checkbox' = 'checkbox',
    'input' = 'input',
    'number' = 'number',
    'textarea' = 'textarea',
    'radio' = 'radio',
    // ...
}

• 在app.componet.html中使用我们创建的dynamic-form

public formConfigs: Array = [
  {
                type: FromItemType.input,
                controlName: 'name',
                label: '姓名',
                required: true
            },
            {
                type: FromItemType.radio,
                controlName: 'sex',
                label: '性别',
                defaultValue: 'man',
                options: [{ label: '男', value: 'man' }, { label: '女', value: 'woman' }, { label: '未知', value: 'unknown' }]
            },
            {
                type: FromItemType.input,
                controlName: 'nationality',
                label: '民族',
                defaultValue: '汉'
            },
            {
                type: FromItemType.number,
                controlName: 'age',
                label: '年龄',
            },
            {
                type: FromItemType.input,
                controlName: 'number',
                label: '学号',
            },
            {
                type: FromItemType.input,
                controlName: 'class',
                label: '班级',
            },
            {
                type: FromItemType.textarea,
                controlName: 'class',
                label: '爱好',
            },
            {
                type: FromItemType.checkbox,
                controlName: 'reConfirm',
                label: '已确认',
                required: true
            }
]

• 根据我们的需要去创建我们需要的表单项

// ***/dynamic-form/elements/
ng g c input
ng g c radio
...

这里以Input为例（这里我还用了ng-zorro），其他的可以看源码。

  {{formConfig.label}}
  
    
  

import { Component, OnInit } from '@angular/core';
import { FormElementBaseClass } from '../../models/form-element-base.class';
import { FromItemConfig } from '../../models/dynamic-form.model';
import { FormGroup } from '@angular/forms';

@Component({
    selector: 'app-input',
    templateUrl: './input.component.html',
    styleUrls: ['./input.component.scss']
})
export class InputComponent {
    public formConfig: FromItemConfig;
    public formGroup: FormGroup;

    public get formControl(): { [key: string]: any } {
        return this.formGroup.controls;
    }
    public constructor() { }
}

• 现在最关键的是dynamic-form.component 的实现

  

    
      

    

    
      
        Submit
      
    
  

import { Component, EventEmitter, Input, OnInit, Output } from '@angular/core';
import { FormBuilder, FormGroup, Validators } from '@angular/forms';
import { FromItemConfig } from '../../models/dynamic-form.model';

@Component({
    selector: 'app-dynamic-form',
    templateUrl: './dynamic-form.component.html',
    styleUrls: ['./dynamic-form.component.scss']
})
export class DynamicFormComponent implements OnInit {

    @Input()
    public formConfigs: Array = new Array();

    public formGroup: FormGroup;

    @Output()
    public readonly submitted: EventEmitter = new EventEmitter();

    public constructor(
        private fb: FormBuilder,
    ) {
        this.formGroup = this.fb.group({});
    }

    public ngOnInit(): void {
        this.setFromControl();
    }

    public submitHandler(): void {
        // tslint:disable-next-line: forin
        for (const i in this.formGroup.controls) {
            this.formGroup.controls[i].markAsDirty();
            this.formGroup.controls[i].updateValueAndValidity();
        }
        if (this.formGroup.valid) {
            this.submitted.emit(this.formGroup.value);
        }
    }
    private setFromControl(): void {
        this.formConfigs?.forEach((control, idx) => {
            this.formGroup.addControl(control.controlName,
                this.fb.control(control.defaultValue || null, control?.required ? Validators.required : null));
        });
    }
}

• 从上面的代码中，我们可以看到一个自定义指令 appDynamicForm，这个自定义指令是最终实现的一个关键。 componentFactoryResolver(动态组件加载器) 和 ViewContainerRef(视图容器)是我们实现的根本。

import { ComponentFactory, ComponentFactoryResolver, ComponentRef, Directive, Input, OnInit, ViewContainerRef } from '@angular/core';
import { FormGroup } from '@angular/forms';
import { NumberComponent } from '../elements/number/number.component';
import { RadioGroupComponent } from '../elements/radio-group/radio-group.component';
import { FromItemConfig } from '../models/dynamic-form.model';
import { CheckboxComponent } from './../elements/checkbox/checkbox.component';
import { InputComponent } from './../elements/input/input.component';
import { TextareaComponent } from './../elements/textarea/textarea.component';

// 通过这个常量将类型和最终指向的组件对应起来
const elementComponent: { [key: string]: any } = {
    checkbox: CheckboxComponent,
    input: InputComponent,
    textarea: TextareaComponent,
    radio: RadioGroupComponent,
    number: NumberComponent,
};

@Directive({
    selector: '[appDynamicForm]'
})
export class DynamicFormDirective implements OnInit {

    @Input()
    public formConfig: FromItemConfig;
    @Input()
    public formGroup: FormGroup;

    private component: ComponentRef;
    public constructor(
        // ComponentFactoryResolver && ViewContainerRef
        private componentFactoryResolver: ComponentFactoryResolver,
        private viewContainerRef: ViewContainerRef,
    ) { }

    public ngOnInit(): void {
        this.viewContainerRef.clear();
        if (!this.formConfig) {
            return;
        }
        const component: any = elementComponent[this.formConfig.type];

        if (!component) {
            return;
        }

        const componentFactory: ComponentFactory = this.componentFactoryResolver.resolveComponentFactory(component);
        const componentRef: ComponentRef = this.viewContainerRef.createComponent(componentFactory);
        componentRef.instance.formConfig = this.formConfig;
        componentRef.instance.formGroup = this.formGroup;
    }
}

至此，动态响应式表单的实现就基本完成了（过程讲的比较粗略），有问题欢迎讨论
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