CODEWITHSUNDEEP
typescript
Simon Hürlimann
Simon Hürlimann

Reputation: 4271

How to access static members from instance methods in typescript?

I try to use a static member from an instance method. I know about accessing static member from non-static function in typescript, but I do not want to hard code the class to allow inheritance:

class Logger {
  protected static PREFIX = '[info]';

  public log(msg: string) {
    console.log(Logger.PREFIX + ' ' + msg); // What to use instead of Logger` to get the expected result?
  }
}

class Warner extends Logger {
  protected static PREFIX = '[warn]';
}

(new Logger).log('=> should be prefixed [info]');
(new Warner).log('=> should be prefixed [warn]');

I've tried things like

typeof this.PREFIX

Upvotes: 38

Views: 31660

Answers (1)

basarat
basarat

Reputation: 276259

You simply need ClassName.property :

class Logger {
  protected static PREFIX = '[info]';
  public log(message: string): void {
    alert(Logger.PREFIX + message); 
  }
}

class Warner extends Logger {
  protected static PREFIX = '[warn]';
}

MORE

from : https://basarat.gitbook.io/typescript/future-javascript/classes

TypeScript classes support static properties that are shared by all instances of the class. A natural place to put (and access) them is on the class itself and that is what TypeScript does:

class Something {
    static instances = 0;
    constructor() {
        Something.instances++;
    }
}

var s1 = new Something();
var s2 = new Something();
console.log(Someting.instances); // 2

UPDATE

If you want it to inherit from the particular instance's constructor use this.constructor. Sadly you need to use some type assertion. I am using typeof Logger shown below:

class Logger {
  protected static PREFIX = '[info]';
  public log(message: string): void {
    var logger = <typeof Logger>this.constructor; 
    alert(logger.PREFIX + message); 
  }
}

class Warner extends Logger {
  protected static PREFIX = '[warn]';
}

Upvotes: 45

Related Questions