是否可以創建一個可以使用多個值來確定我的字段是否有效的驗證器？例如，如果客戶首選的聯系方式是通過電子郵件，則必須填寫電子郵件字段。謝謝。更新了示例代碼...    import {Component, View} from 'angular2/angular2';    import {FormBuilder, Validators, formDirectives, ControlGroup} from 'angular2/forms';    @Component({        selector: 'customer-basic',        viewInjector: [FormBuilder]    })    @View({        templateUrl: 'app/components/customerBasic/customerBasic.html',        directives: [formDirectives]    })    export class CustomerBasic {        customerForm: ControlGroup;        constructor(builder: FormBuilder) {            this.customerForm = builder.group({                firstname: [''],                lastname: [''],                validateZip: ['yes'],                zipcode: ['', this.zipCodeValidator]                 // I only want to validate using the function below if the validateZip control is set to 'yes'            });        }        zipCodeValidator(control) {            if (!control.value.match(/\d\d\d\d\d(-\d\d\d\d)?/)) {                return { invalidZipCode: true };            }        }    }