Here is a scenario where I am using the builder pattern in my code:
export class ValidationBuilderBase implements IValidationBuilder {
public isRequired(): IValidationBuilder {
const validationResult = Validators.required(this.baseControl);
if ((!isNullOrUndefined(validationResult) && !isNullOrUndefined(validationResult.required))) {
this.baseErrors['required'] = 'This input is required.'; // a ValdationErrors instance
}
return this;
}
}
export interface IValidationBuilder {
isRequired(): IValidationBuilder;
}
export class StringValidationBuilder implements IValidationBuilder {
constructor(private readonly builder: Validationbuilderbase) {}
isRequired(): StringValidationBuilder {
return this.builder.isRequired() as StringValidationBuilder;
}
}
// other code, within a function
let builder = new ValidationBuilder(this.formGroup.controls['test']);
let validator: StringValidationBuilder = new StringValidationBuilder(builder);
const result = validator.isRequired(); // expecting the type to be StringValidationBuilder or IValidationBuilder?
During testing with karma jasmine test, validator.isRequired() resolves in a type IValidationBuilder, whereas I was expecting it to be StringValidationBuilder.
This confusion arises because StringValidationBuilder implements the interface and overrides the return type with StringValidationBuilder. So, why is it not returning StringValidationBuilder?
In my IDE (VsCode), the code completion suggests that the return type should be StringValidationBuilder.
Edit
The goal of the following code snippet is to chain string validations:
describe(`String validation chaining`, () => {
it(`should return no errors from the (valid) chain`, () => {
control().setValidators(Validators.required);
control().setValue('This is some test string......');
const result = validator
.string
.ifTrue((val) => false, 'error', 'should not reach here')
.ifFalse((val) => true, 'error', 'should not reach here')
.isRequired()
.maxLengthAllowed(100)
.minLengthAllowed(0)
.range(25, 35)
.build();
expect(result).toEqual(null);
});
});
To make it work, I had to modify the code like this:
export class StringValidationBuilder implements IValidationBuilder {
isRequired(): StringValidationBuilder {
this.builder.isRequired();
return this;
}
}
Although this modification made the code work, I still have doubts about whether this is the ideal solution.