Angular service for getting Data in API rest

I write my first Angular App and I want to get Data from another API Rest available in local.

My work based on Angular tuto tour-of-heroes. I use a component service for calling my API and return result in another component. I don't know how debug correctly in Angular. My API Rest run correctly and return data if call with my browser.

My component datatable (which display return data API) run correctly and display HTML but not the *ngFor part (tr table for each data).

If you have a trick for helping debug or find where is error...

app.component.ts

import {Component} from '@angular/core';

@Component({
    selector: 'app-my-app',
    template: `
        <h1>fzfzefzfzefz</h1>
        <nav>
        </nav>
        <app-my-datatable></app-my-datatable>
        <!--<router-outlet></router-outlet>-->
    `,
    styleUrls: ['./app.component.css']
})

export class AppComponent {
    title = 'blablabla';
}

app.module.ts

import { BrowserModule }      from '@angular/platform-browser';
import { NgModule }           from '@angular/core';
import { FormsModule }        from '@angular/forms';
import {Router, RouterModule} from '@angular/router';

import { AppComponent }       from './app.component';
import { DatatableComponent } from './datatable.component';
import { OperationService }   from './operation.service';

import { AppRoutingModule }   from './app-routing.module';
import { HttpModule }         from '@angular/http';

@NgModule({
  declarations: [AppComponent, DatatableComponent],
  imports:      [
      BrowserModule,
      FormsModule,
      AppRoutingModule,
      HttpModule,
      RouterModule.forRoot([{path: 'datatable', component: DatatableComponent}])
  ],
  providers:    [
      OperationService
  ],
  bootstrap:    [AppComponent]
})

export class AppModule { }

app-routing.module.ts

import { NgModule }             from '@angular/core';
import { RouterModule, Routes } from '@angular/router';

import {DatatableComponent}     from './datatable.component';

const routes: Routes = [
    { path: '', redirectTo: '/datatable', pathMatch: 'full' },
    { path: 'datatable',  component: DatatableComponent },
];

@NgModule({
    imports: [ RouterModule.forRoot(routes) ],
    exports: [ RouterModule ]
})

export class AppRoutingModule {}

datatable.component.html

<h1>efzefzefz</h1>

<table>
    <thead>
        <tr>
            <th>ID</th>
            <th>Label</th>
            <th>Cost</th>
        </tr>
    </thead>
    <tbody>
        <tr *ngFor="let operation of operations">
            <td>1</td>
            <td>2</td>
            <td>3</td>
        </tr>
    </tbody>
</table>

datatable.component.ts

import { Component, OnInit } from '@angular/core';

import { Operation }         from './operation';
import { OperationService }  from './operation.service';

@Component({
    selector: 'app-my-datatable',
    templateUrl: './datatable.component.html',
    styleUrls: ['./datatable.component.css']
})

export class DatatableComponent implements OnInit{

    title = 'app toto';

    operations: Operation[];

    constructor(private operationService: OperationService) { }

    getOperations(): void {
        this.operationService.getOperations().then(operations => this.operations = operations);
    }
    ngOnInit(): void {
        this.getOperations();
    }
}

operations.service.ts

import { Injectable }       from '@angular/core';
import { Headers, Http }    from '@angular/http';

import { Operation }        from './operation';

import 'rxjs/add/operator/toPromise';

@Injectable()

export class OperationService
{
    private headers = new Headers({'Content-Type': 'application/json'});
    private operationsUrl = 'http://60.60.60.100/api/operations';

    constructor(private http: Http) { }

    getOperations(): Promise<Operation[]>
    {
        return this.http.get(this.operationsUrl)
            .toPromise()
            .then(response => response.json().data as Operation[])
            .catch(this.handleError);
    }

    getOperation(id: number): Promise<Operation>
    {
        const url = `${this.operationsUrl}/${id}`;
        return this.http.get(url)
            .toPromise()
            .then(response => response.json().data as Operation)
            .catch(this.handleError);
    }

    update(operation: Operation): Promise<Operation>
    {
        const url = `${this.operationsUrl}/${operation.id}`;
        return this.http
            .put(url, JSON.stringify(operation), {headers: this.headers})
            .toPromise()
            .then(() => operation)
            .catch(this.handleError);
    }

    create(name: string): Promise<Operation>
    {
        return this.http
            .post(this.operationsUrl, JSON.stringify({name: name}), {headers: this.headers})
            .toPromise()
            .then(res => res.json().data as Operation)
            .catch(this.handleError);
    }

    delete(id: number): Promise<void>
    {
        const url = `${this.operationsUrl}/${id}`;
        return this.http.delete(url, {headers: this.headers})
            .toPromise()
            .then(() => null)
            .catch(this.handleError);
    }

    private handleError(error: any): Promise<any> {
        console.error('An error occurred', error); // for demo purposes only
        return Promise.reject(error.message || error);
    }
}

thanks for help.