Angular 2.3 组件继承和依赖注入

Question

如何使用新的 Angular 2.3 组件继承在子组件和父组件之间共享依赖注入。

例如我想将 AlertService 下移到父组件中，并将 TraingCompanyService 留在派生组件中

当前组件

@Component({
    selector: 'wk-training-company-edit',
    template: require('./edit.html')
})
export class TrainingCompanyEditComponent implements OnInit, OnDestroy {

    constructor(
                private alert: AlertService,
                private trainingCompanyService: TrainingCompanyService
                ) {

    }
}

重构组件 (V1)

在派生类的构造函数中调用this之前必须调用super

@Component({
    selector: 'wk-training-company-edit',
    template: require('./edit.html')
})
export class TrainingCompanyEditComponent extends BaseAdminEditComponent implements OnInit, OnDestroy {

    constructor(
                private alert: AlertService,
                private trainingCompanyService: TrainingCompanyService
                ) {

        // Error: Super must be called before calling this in the constructor of the derived class
        super(this.alert);
    }
}

export class BaseAdminEditComponent {

    constructor(private alert: AlertService) {
    }

    protected handleSaveError(error: any) {

        if (error.message) {
            if (error.errors && _.isArray(error.errors) && error.errors.length > 0) {
                this.alert.error(_.join(error.errors, '\n'), error.message);
            }
            else {
                this.alert.error(error.message);
            }
        }
    }
}

重构组件 (V2)

类 TrainingCompanyEditComponent 错误地扩展了基类 BaseAdminEditComponent，类型有单独的私有属性 'alert' 声明

@Component({
    selector: 'wk-training-company-edit',
    template: require('./edit.html')
})
export class TrainingCompanyEditComponent extends BaseAdminEditComponent implements OnInit, OnDestroy {

    // Class TrainingCompanyEditComponent incorrectly extends base class BaseAdminEditComponent, types have seperate declarations of private property 'alert'
    constructor(
                private alert: AlertService,
                private trainingCompanyService: TrainingCompanyService
                ) {

        // alert instead of this.alert
        super(alert);
    }
}

export class BaseAdminEditComponent {

    constructor(private alert: AlertService) {
    }

    protected handleSaveError(error: any) {

        if (error.message) {
            if (error.errors && _.isArray(error.errors) && error.errors.length > 0) {
                this.alert.error(_.join(error.errors, '\n'), error.message);
            }
            else {
                this.alert.error(error.message);
            }
        }
    }
}

重构组件 (V3)

这行得通，只是想知道它是否是最好的技术

@Component({
    selector: 'wk-training-company-edit',
    template: require('./edit.html')
})
export class TrainingCompanyEditComponent extends BaseAdminEditComponent implements OnInit, OnDestroy {

    // Class TrainingCompanyEditComponent incorrectly extends base class BaseAdminEditComponent, types have seperate declarations of private property 'alert'
    constructor(
                private alert: AlertService,
                private trainingCompanyService: TrainingCompanyService
                ) {

        // alert instead of this.alert
        super(alert);
    }
}

export class BaseAdminEditComponent {

    // Create a private variable with a different name, e.g. alert2
    private alert2: AlertService;

    constructor(alert: AlertService) {
        this.alert2 = alert;
    }

    protected handleSaveError(error: any) {

        if (error.message) {
            if (error.errors && _.isArray(error.errors) && error.errors.length > 0) {
                this.alert2.error(_.join(error.errors, '\n'), error.message);
            }
            else {
                this.alert2.error(error.message);
            }
        }
    }

}

Answer 1

只需将派生类中构造函数参数的访问修饰符设置为与基类中相同的级别即可。即

基类

import * as _ from "lodash";

import {AlertService} from '../common/alert/alert.service';

export class BaseAdminEditComponent {

    constructor(protected alert: AlertService) { }

    protected handleSaveError(error: any) {

        if (error.message) {
            if (error.errors && _.isArray(error.errors)) {
                console.error(error.errors);
            }
            this.alert.error(error.message);
        }
    }
}

派生类

@Component({
    selector: 'wk-training-company-edit',
    template: require('./edit.html')
})
export class TrainingCompanyEditComponent extends BaseAdminEditComponent {

    trainingCompany: TrainingCompany;

    trainingCompanyId: number;

    constructor(
        protected alert: AlertService,
        private validation: ValidationService,
        private trainingCompanyService: TrainingCompanyService) {

        super(alert);

        // Other Constructor Code Here
    }
}

Answer 2

我终于找到了可行的模式，重要的是不要使用 Radim 在构造函数中提到的私有（语法糖模式）。

我将警报服务设置为基类上的受保护属性。

将基本事件处理程序绑定到此handlerSaveError.bind(this) 很重要

最终的工作代码在这里。

基类

import * as _ from "lodash";

import {AlertService} from '../common/alert/alert.service';

export class BaseAdminEditComponent {

    protected alert: AlertService;

    constructor(alert: AlertService) {
        this.alert = alert;
    }

    protected handleSaveError(error: any) {

        if (error.message) {
            if (error.errors && _.isArray(error.errors)) {
                console.error(error.errors);
            }
            this.alert.error(error.message);
        }
    }
}

组件实例类

@Component({
    selector: 'wk-training-company-edit',
    template: require('./edit.html')
})
export class TrainingCompanyEditComponent extends BaseAdminEditComponent {

    trainingCompany: TrainingCompany;

    trainingCompanyId: number;

    constructor(alert: AlertService, // Don't use private property
                private validation: ValidationService,
                private trainingCompanyService: TrainingCompanyService) {

        super(alert);

        // Other Constructor Code Here
    }

    onSave($event) {

        console.log('Save TrainingCompany');

        this.trainingCompany = TrainingCompany.fromJson(this.form.value);

        console.log(JSON.stringify(this.trainingCompany, null, 2));

        var isNew = _.isNil(this.trainingCompany.id);

        this.trainingCompanyService
            .upsert$(this.trainingCompany)
            .subscribe((response: EntityResponse<TrainingCompany>) => {

                try {
                    this.alert.success('TrainingCompany updated');

                    this.modelChange.fire('training-company', isNew ? 'new' : 'update', this.trainingCompany);
                }
                catch (e) {
                    console.error(e);
                    throw e;
                }
            }, this.handleSaveError.bind(this)); // Common Error Handler from base class. NOTE: bind(this) is required

    }
}

Answer 3

带有类似这样修饰符关键字的构造函数定义

export class TrainingCompanyEditComponent 
    extends BaseAdminEditComponent implements OnInit, OnDestroy {

    constructor(
        private alert: AlertService,
        private trainingCompanyService: TrainingCompanyService
    ) {
    }
    ...

只是更详细的语法糖：

export class TrainingCompanyEditComponent 
    extends BaseAdminEditComponent implements OnInit, OnDestroy {

    private alert: AlertService,
    private trainingCompanyService: TrainingCompanyService

    constructor(
        alert: AlertService,
        trainingCompanyService: TrainingCompanyService
    ) {
        this.alert = alert; // assign incoming value to member
        this.trainingCompanyService = trainingCompanyService;
    }
    ...

所以，这是在后台。我们只能在调用 super 后执行该分配。这就是为什么我们必须将使用 this.alert （访问成员） 的调用更改为 alert （传递传入值）

    constructor(
        private alert: AlertService,
        private trainingCompanyService: TrainingCompanyService
    ) {
        //super(this.alert);
        super(alert); // this.alert was not assign yet

        // next ?
        // the this.alert will be assigned for us...
    }

玩这个adjusted definition here

Answer 4

尝试将构造函数移动到 BaseAdminEditComponent 中，而不是覆盖 TrainingCompanyEditComponent 中的构造函数。

@Component({
    selector: 'wk-training-company-edit',
    template: require('./edit.html')
})
export class TrainingCompanyEditComponent extends BaseAdminEditComponent implements OnInit, OnDestroy {

    
}

export class BaseAdminEditComponent {

    constructor(private alert: AlertService,
                private trainingCompanyService: TrainingCompanyService) {
    }

    protected handleSaveError(error: any) {

        if (error.message) {
            if (error.errors && _.isArray(error.errors) && error.errors.length > 0) {
                this.alert.error(_.join(error.errors, '\n'), error.message);
            }
            else {
                this.alert.error(error.message);
            }
        }
    }
}