打字稿：静态方法返回值

Question

I have such class:

export class GlobalValidation {
    static emailPattern(control: AbstractControl): ValidationResult {
        var EMAIL_REGEXP = Pattern.EMAIL;
        return this.checkPattern(control, EMAIL_REGEXP);
    }

    static urlPattern(control: AbstractControl): ValidationResult {
        var URL_REGEXP = Pattern.URL;
        return this.checkPattern(control, URL_REGEXP);
    }

    static checkPattern(control: AbstractControl, pattern: any) {
        if (control.value != "" && !pattern.test(control.value)) {
            return {"incorrectPatternFormat": true};
        }

        return null;
    }
}

EXCEPTION: Uncaught (in promise): Error: Error in :0:0 caused by: Cannot read property 'checkPattern' of undefined TypeError: Cannot read property 'checkPattern' of undefined at GlobalValidation.urlPattern

What am I doing wrong?

When I rewrite class to this:

export class GlobalValidation {

    static emailPattern(control: AbstractControl): ValidationResult {

        var EMAIL_REGEXP = Pattern.EMAIL;

        if (control.value != "" && !URL_REGEXP.test(control.value)) {
            return {"incorrectPatternFormat": true};
        }

        return null;
    }


    static urlPattern(control: AbstractControl): ValidationResult {

        var URL_REGEXP = Pattern.URL;

        if (control.value != "" && !URL_REGEXP.test(control.value)) {
            return {"incorrectPatternFormat": true};
        }

        return null;
    }
}

Everything is fine.

Seems that something is obvious, but I miss it.

Answer 1

You are calling checkPattern using this , albeit it being a static method. Call checkPattern using GlobalValidation.checkPattern(...)

Answer 2

You can't access this from static method. Using static classes has one purpose and that is - you don't need to create a new instance of the class to use the method.

You should use GlobalValidation.checkPatter(...) as Phil Cap suggested or just rewrite it, so it doesn't use the properties of GlobalValidation class.