In my development project, I have defined a couple of interface types and a union type:
export interface FieldOptions {
value: string | number;
viewValue: string;
}
export interface BaseField {
id: string;
derived?: boolean;
required?: boolean;
}
export interface NumberField extends BaseField {
type: 'number';
decimals: number;
}
export interface SelectField extends BaseField {
type: 'select' | 'select-multi';
options: FieldOptions[];
source?: string;
}
export type Field = NumberField | SelectField;
I've come across an issue with the usage of the union type Field. It means that a field can be either a Number or a Select.
To handle this situation, I've implemented a function in my Angular Component:
getField( key: string ): Field {
return this.fields.filter( el => el.id === key )[ 0 ];
}
getFieldVersion2( key: string ): any {
const field = this.fields.filter( el => el.id === key )[ 0 ];
if ( (field as SelectField).options ) {
return field as SelectField;
} else {
return field as Field;
}
}
When using only the function getField in my template to retrieve a Field object, specifically a Select with an Options array of view/viewValues, I encounter a TypeScript error:
Property 'options' does not exist on type 'Field'.
Property 'options' does not exist on type 'NumberField'.
My understanding is that Field is a union type of either Number or Select, where one has an options property and the other doesn't.
To address this issue, I introduced getFieldVersion2 in hopes of resolving it. However, unless I specify the result type as any, it will result in a build error.
The specific section of the template causing the compile error due to the use of options:
<mat-form-field class="input">
<mat-select formControlName="state">
<mat-option *ngFor="let option of getField( 'state' ).options" [value]="option.value">
{{option.viewValue}}
</mat-option>
</mat-select>
</mat-form-field>
In light of this situation, what could be a better approach to handling this scenario?