如何从另一个组件Angular2调用方法

我是angular2的新手2，这就是为什么我需要帮助我正在创建多步骤形式，我需要从另一个组件调用方法我在此组件模板中有sallcomponent，我有

<sell-wizard>
  <sell-wizard-step></sell-wizard-step>
</sell-wizard>

我必须调用位于wizardcomponent中的方法以下来自组件的代码

wizardComponent

import { Component, Input, Output, EventEmitter } from '@angular/core';
@Component({
selector: 'sell-wizard',
template: "
<ng-content></ng-content>
<div
  class="my-wizard__footer">
  <button
    [style.visibility]="isOnFirstStep() ? 'hidden' : 'visible'"
    (click)="stepChange.emit(step - 1)">
    Previous
  </button>
  {{step}} / {{steps}}
  <button
    *ngIf="!isOnFinalStep()"
    (click)="stepChange.emit(step + 1)">
    Next
  </button>
  <button
    *ngIf="isOnFinalStep()"
    (click)="finish.emit(step + 1)">
    {{finishText}}
  </button>
</div>",
})
export class WizardComponent {
@Input() finishText = 'Finish';
@Input() step = 1;
@Output() finish = new EventEmitter();
@Output() stepChange = new EventEmitter();
private steps = 0;
private isOnFinalStep = () => this.step === this.steps;
private isOnFirstStep = () => this.step === 1;
public addStep() {
  const newSteps = this.steps + 1;
  this.steps = newSteps;
  return newSteps;
}}

wizardstepcomponent

import { Component, Input } from '@angular/core';
import { WizardComponent } from './wizard.component';
@Component({
  selector: 'sell-wizard-step',
  host: {
    '[style.display]': 'isCurrent ? "block" : "none"',
  },
  template: `<ng-content></ng-content>`,
})
export class WizardStepComponent {
private isCurrent;
private step;
constructor(
  private parent:WizardComponent
  ) {}
ngOnInit() {
  this.step = this.parent.addStep();
  this.isCurrent = this.step === this.parent.step;
  this.parent.stepChange.subscribe(step => {
    this.isCurrent = this.step === step;
  });
 }
}

SellComponent

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

@Component({
  moduleId: module.id,
  selector: 'sell',
  templateUrl: 'sell.component.html'
})
export class SellComponent  {
  private step = 1;
  constructor(){}
}

所以在这个sellcomponent视图中，我尝试从wizardcomponent调用方法

<button type="button" (click)="stepChange.emit(step + 1)">next</button>

说Cannot read property 'stepChange' of undefined我如何从另一个组件中调用fucntion？感谢您的帮助