mycomponent.component.ts

// imports..
@Component({
  // same same ...
})
export class MyComponent implements OnInit {
  public form: FormGroup;
  
  constructor(private config: MyService) {}

  ngOnInit() {
    this.config.init();
    this.form = this.config.form.general;
  }
  
  // update form
  update() {
    let formdata = [];
    Object.keys(this.form.value).forEach(k => {
      // ibabalik ko parse to decimal
      if(k == 'field1') { this.form.value[k] = this.form.value[k] / 100 }
      formdata.push({slug: k, value: this.form.value[k]})
    });
    
    // Eto yung medyo special na part. kasi di ko alam kung okay ba na practice tong pag pasa
    // ng callback sa function ng service.
    this.config.update(formdata, res => {
      alert(res.message);
    });
  }
}

myhtml.component.html

<form [formGroup]="form" (ngSubmit)="update()">
  <div class="row">
    <div class="form-group col-md-3">
      <label>Field1:</label>
      <input
        formControlName="field1" 
        type="text" class="form-control">
    </div>
  </div>
  <button type="submit" class="btn btn-warning">Update Changes</button>
</form>

myservice.service.ts

// imports ... 
@Injectable()
export class MyService {
    constructor(private http: Http) { }
    public form = {
        general: new FormGroup({
            "field1": new FormControl(0, Validators.required)
        })
    };
    
    init() {
        this.getAll()
        .subscribe(data => {
            data.forEach(row => {
                // kung field1 ang nakuha na row gagawin kong whole number ang value.
                if( row.slug == 'field1') { row.value = row.value * 100 }
                this.form.general.get(row.slug).setValue(row.value);
            });
        });
    }
    
    // get values from server. e.g response [{slug: 'field1', value: '.2'}]
    getAll() {
        return this.http.get('/v1/url')
        .map(res => res.json());
    }
    
    //update given callback.
    // callback is for the subscribe function.
    update(formdata, callback) {
    return this.http
      .put('v1/url/update', {data: formdata})
      .map(res => res.json())
      .subscribe(callback) // dito ko tinawag si callback
    }
}