generics.ts

interface Decoder<A> {
  decode(source: string): A;
}

class NumDecoder implements Decoder<Number> {
	decode(source: string): Number {
		return Number(source.trim());
	}
}

class StringDecoder implements Decoder<string> {
	decode(source: string): string {
		return source.trim();
	}
}

class ListDecoder<A> implements Decoder<A[]> {
	constructor(public itemDecoder: Decoder<A>) {}
	
	decode(source: string): A[] {
		var ss: string[] = source.split(',');
		return ss.map(this.itemDecoder.decode);
	}
}

var numDecoder:     Decoder<Number>   = new NumDecoder();
var strDecoder:     Decoder<string>   = new StringDecoder();
var numListDecoder: Decoder<Number[]> = new ListDecoder(numDecoder);

alert(String(numDecoder.decode("019")));
alert(strDecoder.decode("hogera"));
alert(String(numListDecoder.decode(" 10 ,   20 ,  30 ")));