In this lesson we‘re going to learn how to dynamically hide a form control with Formly‘s hideExpressions. These expressions are evaluated automatically at runtime whenever a change on our form happens. As a result we can easily hide - say - the city dropdown field when no nation value has been selected yet.
{ key: ‘cityId‘, type: ‘select‘, templateOptions: { label: ‘Cities‘, options: [], }, expressionProperties: { ‘templateOptions.disabled‘: model => !model.nationId, ‘model.cityId‘: ‘!model.nationId ? null: model.cityId‘, }, hideExpression: model => { return !model.nationId; }, hooks: { onInit: (field: FormlyFieldConfig) => { field.templateOptions.options = field.form.get(‘nationId‘).valueChanges.pipe( startWith(this.model.nationId), switchMap(nationId => this.dataService.getCities(nationId)), ); }, }, },
[ngx-formly] Dynamically hide Form Controls with Angular Formly
原文：https://www.cnblogs.com/Answer1215/p/12172130.html