in docs-content/examples-source/material/form-field/form-field-custom-control/form-field-custom-control-example.ts [190:200]
onContainerClick() {
if (this.parts.controls.subscriber.valid) {
this._focusMonitor.focusVia(this.subscriberInput, 'program');
} else if (this.parts.controls.exchange.valid) {
this._focusMonitor.focusVia(this.subscriberInput, 'program');
} else if (this.parts.controls.area.valid) {
this._focusMonitor.focusVia(this.exchangeInput, 'program');
} else {
this._focusMonitor.focusVia(this.areaInput, 'program');
}
}