我是 React 新手，遇到了如下问题：

Uncaught TypeError: Cannot read property 'setState' of null.

基本上，我想做的是，用户可以点击三个不同的标题，点击后，它将呈现特定于该标题的特定模板。这是我当前使用的代码，它给了我这个错误：

class Selection extends React.Component {

constructor(props) {
    super(props);
    this.state = {selections: [], donateActive: true, fundraiseActive: false, speakActive: false };
}

componentDidMount() {
    this.setState({
        selections: selectionData.selections
    })
}

componentWillUnMount(){
    console.log("unmounted!"); 
}

donateOnClick() {
    this.setState({ donateActive: true, fundraiseActive: false, speakActive: false});
}

fundraiseOnClick() {
    this.setState({ fundraiseActive: true, donateActive: false, speakActive: false});
}

speakOnClick() {
    this.setState({ speakActive: true, fundraiseActive: false, donateActive: false});
}

donateTemplate() {
    return (
        <div>
            <h1>donate template</h1>
        </div>
    )
}   

fundraiseTemplate() {
    return (
        <div>
            <h1>fundraise template</h1>
        </div>
    )

}

speakTemplate() {
    return (
        <div>
            <h1>speak template</h1>
        </div>
    )
}

render() {
    return(
        <div>
            <div className="col-sm-6 col-sm-push-6 right">
                <div className="right-content-container">
                    <div className="selections">
                        <h3>You can</h3>
                        <h1 onClick={this.donateOnClick} className="selection active" id="selection-donate">donate</h1>
                        <h1 onClick={this.fundraiseOnClick} className="selection" id="selection-fundraise">fundraise</h1>
                        <h1 onClick={this.speakOnClick} className="selection" id="selection-speak">speak up</h1>
                        <hr></hr>
                    </div>
                    <div>
                        {
                            if (this.state.donateActive) {
                                this.donateTemplate()
                            }
                            if (this.state.fundraiseActive) {
                                this.fundraiseTemplate()
                            }
                            if (this.state.speakActive) {
                                this.speakTemplate()
                            }
                        }
                    </div>
                </div>
            </div>
            <div className="col-sm-6 col-sm-pull-6 left">
                <div className="left-content-container">
                    <img className="img-responsive hidden-xs" src="./images/selections/.jpg" alt=""/>
                    <img className="img-responsive hidden-sm hidden-md hidden-lg" src="./images/selections/.jpg" alt=""/>
                </div>
            </div>
        </div>
    );
}


}

此外，我不确定我是否能够像现在在 render() 方法中那样在 return() 中使用 IF 语句，有没有更好的方法来做到这一点？

任何帮助都将不胜感激。