React Native初始化对象问题

export default class Loop {

props: {
    onLoop(item): Function;
}

loopBody = [];
point = 0;

create(body) {
    this.loopBody = body;
    if (this.props.onLoop) {
        this.props.onLoop(this.loopBody[this.point]);
    }
}

next() {
    this.point += 1;
    if (this.point == this.loopBody.length) {
        this.point = 0;
    }
    if (this.props.onLoop) {
        this.props.onLoop(this.loopBody[this.point]);
    }
}

}

我写了一个这样的类。如下初始化这个类。可以通过let l=new Loop();但是如何使用到onLoop(item)这个属性？

l.onLoop(item)?