共享服务：

@Injectable()
export class SharedService {
 
    componentOneFn: Function;
 
    constructor() { }
}

第一部分：

export class ComponentOne {
 
    name: string = 'Component one';
 
    constructor(private sharedService: SharedService) {
        this.sharedService.componentOneFn = this.sayHello;
    }
 
    sayHello(callerName: string): void {
        console.log(`Hello from ${this.name}. ${callerName} just called me!`);
    }
}

第二部分：

export class ComponentTwo {
 
    name: string = 'Component two';
 
    constructor(private sharedService: SharedService) {
        if(this.sharedService.componentOneFn) {
            this.sharedService.componentOneFn(this.name); 
            // => Hello from Component one. Component two just called me!
        }
    }
}

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