2017-05-24 10 views
1

Ich versuche, React Rechner zu bauen. Bis jetzt funktioniert es nur, wenn die Länge meiner zweiten Nummer gleich 1 ist. Wenn es mehr Ziffern ist, wird es brechen. Hier ist der Code:React Calculator

class Calculator extends Component { 
    constructor(props) { 
     super(props); 
     this.state = { 
     current: 0, 
     total: 0, 
     operator: '' 
     }; 
    } 
    handleType = (e) =>{ 
    const current = (this.state.current == 0 || this.state.operator != '' || this.state.current == this.state.total) ? '' : this.state.current 
    this.setState({ 
     current: parseInt(current + e.target.attributes.getNamedItem('data-filter').value) 
    }); 
    } 
calculate = (sign, number) => { 
    const total = this.state.total; 
    console.log(total); 
    switch(sign){ 
    case "-": 
     return total - number; 
     break; 
    case "+": 
     return total + number; 
     break; 
    case "*": 
     return total * number; 
     break; 
    case "/": 
     return total/number; 
     break; 
    default: 
     return 0; 
    } 
}; 

handleAction = (e) =>{ 
    const operator = e.target.attributes.getNamedItem('data-filter').value; 
    console.log(operator); 
    this.setState({ 
    total: this.state.current, 
    operator: operator 
    }); 
    console.log(this.state); 
} 
getResult =() =>{ 
    this.setState({ 
    current: this.calculate(this.state.operator, this.state.current) 
    }); 
} 

    render() { 
    return (
     <div className="Calculator text-center"> 
      <h2>Result: {this.state.current} </h2> 
      <div className="row"> 
       <button data-filter="7" onClick={this.handleType}>7</button> 
       <button data-filter="8" onClick={this.handleType} >8</button> 
       <button data-filter="9" onClick={this.handleType} >9</button> 
       <button data-filter="+" onClick ={this.handleAction} >+</button> 
      </div> 
      <div className="row"> 
       <button data-filter="4" onClick={this.handleType}>4</button> 
       <button data-filter="5" onClick={this.handleType}>5</button> 
       <button data-filter="6" onClick={this.handleType}>6</button> 
       <button data-filter="-" onClick ={this.handleAction} >-</button> 
      </div> 
      <div className="row"> 
       <button data-filter="1" onClick={this.handleType}>1</button> 
       <button data-filter="2" onClick={this.handleType}>2</button> 
       <button data-filter="3" onClick={this.handleType}>3</button> 
       <button data-filter="*" onClick ={this.handleAction} >*</button> 
       <button data-filter="/" onClick ={this.handleAction} >/</button> 
      </div> 
      <div className="row"> 
       <button>0</button> 
       <button>save</button> 
       <button>cancel</button> 
       <button onClick={this.getResult}>=</button> 
      </div> 

     </div> 
    ); 
    } 
} 

Ich verstehe, dass das Problem ist mein Zustand:

const current = (this.state.current == 0 || this.state.operator != '' || this.state.current == this.state.total) ? '' : this.state.current 

Es funktioniert gut für die erste Zahl, wenn Operator = ‚‘, aber sobald ich einen Operator haben wird es nicht erlauben sie mir, meine Nummer größer als 9

hier zu machen, ist die codepen Demo http://codepen.io/polinaz/pen/PmLoKJ?editors=0010

Irgendwelche Ideen, wie man es beheben? Danke :)

+0

denke ich, die Verbindung des Demo falsch ist – Sheng

+0

Sorry about this! Jetzt aktualisiert – Polina

Antwort

1

ich eine Reihe von Änderungen im Code vorgenommen habe:

als staatliches Updates asynchron sein kann (https://facebook.github.io/react/docs/state-and-lifecycle.html#state-updates-may-be-asynchronous), dann ist es sehr schlechte Praxis So verwenden Sie vorherige Statuswerte in der von Ihnen verwendeten Weise:

this.setState({ 
    current: parseInt(current + e.target.attributes.getNamedItem('data-filter').value) 
}); 

Ich habe eine Reihe von ihnen in dieses Format ändern:

this.setState((prevState) => { 
    const current = prevState.current; 
    return {current: parseInt(current + value)}; 
}); 

Ich zog den e.target.attributes.getNamedItem('data-filter').value Code in seine eigene Variable aufgrund event-pooling

handleType (e) { 
    const value = e.target.attributes.getNamedItem('data-filter').value; 

Der größte Fehler, den Sie war konfrontiert waren, nach dem Operator ausgewählt wurde (über handleAction), wurde Ihr Operatorattribut ausgefüllt. Dieser Mittelwert in Ihrem handleType, haben Sie die Kontrolle: this.state.operator != ''

const current = (this.state.current == 0 || this.state.operator != '' || this.state.current == this.state.total) ? '' : this.state.current 

Dies bedeutete Sie den zuvor ausgewählten Stromwert wurden zu vernachlässigen. setze es auf '' und lege es dann an den aktuellen Wert an.

class Calculator extends React.Component { 
 
    constructor(props) { 
 
     super(props); 
 
     this.state = { 
 
     current: 0, 
 
     total: 0, 
 
     operator: '' 
 
     }; 
 
    this.handleType = this.handleType.bind(this); 
 
    this.calculate = this.calculate.bind(this); 
 
    this.handleAction = this.handleAction.bind(this); 
 
    this. getResult = this.getResult.bind(this); 
 
    
 
    } 
 
    
 
    handleType (e) { 
 
    const value = e.target.attributes.getNamedItem('data-filter').value; 
 

 
    this.setState((prevState) => { 
 
     const current = (this.state.current == 0 || this.state.current == this.state.total) ? '' : this.state.current; 
 
     return {current: parseInt(current + value)}; 
 
    }); 
 
     
 
    } 
 
calculate (sign, number) { 
 
    const total = this.state.total; 
 
    console.log(total); 
 
    switch(sign){ 
 
    case "-": 
 
     return total - number; 
 
     break; 
 
    case "+": 
 
     return total + number; 
 
     break; 
 
    case "*": 
 
     return total * number; 
 
     break; 
 
    case "/": 
 
     return total/number; 
 
     break; 
 
    default: 
 
     return 0; 
 
    } 
 
}; 
 

 
handleAction (e) { 
 
    const operator = e.target.attributes.getNamedItem('data-filter').value; 
 
    
 
    this.setState((prevState) => { 
 
    return { 
 
    total: prevState.current, 
 
    operator: operator, 
 
    current: 0 
 
    } 
 
    }); 
 
    
 
    console.log(this.state); 
 
} 
 
getResult() { 
 
    this.setState({ 
 
    current: this.calculate(this.state.operator, this.state.current) 
 
    }); 
 
} 
 

 
    render() { 
 
    return (
 
     <div className="Calculator text-center"> 
 
      <h2>Result: {this.state.current} </h2> 
 
      <div className="row"> 
 
       <button data-filter="7" onClick={this.handleType}>7</button> 
 
       <button data-filter="8" onClick={this.handleType} >8</button> 
 
       <button data-filter="9" onClick={this.handleType} >9</button> 
 
       <button data-filter="+" onClick ={this.handleAction} >+</button> 
 
      </div> 
 
      <div className="row"> 
 
       <button data-filter="4" onClick={this.handleType}>4</button> 
 
       <button data-filter="5" onClick={this.handleType}>5</button> 
 
       <button data-filter="6" onClick={this.handleType}>6</button> 
 
       <button data-filter="-" onClick ={this.handleAction} >-</button> 
 
      </div> 
 
      <div className="row"> 
 
       <button data-filter="1" onClick={this.handleType}>1</button> 
 
       <button data-filter="2" onClick={this.handleType}>2</button> 
 
       <button data-filter="3" onClick={this.handleType}>3</button> 
 
       <button data-filter="*" onClick ={this.handleAction} >*</button> 
 
       <button data-filter="/" onClick ={this.handleAction} >/</button> 
 
      </div> 
 
      <div className="row"> 
 
       <button data-filter="0" onClick={this.handleType}>0</button> 
 
       <button>save</button> 
 
       <button>cancel</button> 
 
       <button onClick={this.getResult}>=</button> 
 
      </div> 
 

 
     </div> 
 
    ); 
 
    } 
 
} 
 

 
ReactDOM.render(
 
    <Calculator/>, 
 
    document.getElementById('root') 
 
);
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script> 
 
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script> 
 

 
<div id='root'></div>

+0

Vielen Dank für eine großartige Erklärung !! Es ist jetzt viel klarer für mich! – Polina

1

Haben einige Änderungen, siehe das Snippet.

Arbeits Snippet:

class Calculator extends React.Component { 
 
    constructor(props) { 
 
     super(props); 
 
     this.state = { 
 
     current: '', 
 
     total: 0, 
 
     operator: '' 
 
     }; 
 
    } 
 

 
    handleType = (e) =>{ 
 
    const current = (this.state.current == 0 || this.state.operator != '' || this.state.current == this.state.total) ? '' : this.state.current 
 
    this.setState({ 
 
     current: this.state.current + e.target.attributes.getNamedItem('data-filter').value 
 
    }); 
 
    } 
 

 
    calculate() { 
 
    const total = parseInt(this.state.total); 
 
    const current = parseInt(this.state.current); 
 
    const sign = this.state.operator; 
 
    switch(sign){ 
 
     case "-": 
 
     return total - current; 
 
      break; 
 
     case "+": 
 
      return total + current; 
 
      break; 
 
     case "*": 
 
      return total * current; 
 
      break; 
 
     case "/": 
 
      return total/current; 
 
      break; 
 
     default: 
 
      return 0; 
 
    } 
 
    }; 
 

 
    handleAction = (e) =>{ 
 
    const operator = e.target.attributes.getNamedItem('data-filter').value; 
 
    this.setState({ 
 
     total: this.state.current, 
 
     current: '', 
 
     operator: operator 
 
    }); 
 
    } 
 

 
    getResult =() => { 
 
    this.setState({ 
 
     total: this.calculate(), 
 
     current: '' 
 
    }); 
 
    } 
 
    
 
    cancel =() => { 
 
    this.setState({ 
 
     total: '', 
 
     current: '', 
 
     operator: '' 
 
    }) 
 
    } 
 

 
    render() { 
 
    return (
 
     <div className="Calculator text-center"> 
 
      Number: {this.state.current} 
 
      <h2>Result: {this.state.total} </h2> 
 
      <div className="row"> 
 
       <button data-filter="7" onClick={this.handleType}>7</button> 
 
       <button data-filter="8" onClick={this.handleType} >8</button> 
 
       <button data-filter="9" onClick={this.handleType} >9</button> 
 
       <button data-filter="+" onClick ={this.handleAction} >+</button> 
 
      </div> 
 
      <div className="row"> 
 
       <button data-filter="4" onClick={this.handleType}>4</button> 
 
       <button data-filter="5" onClick={this.handleType}>5</button> 
 
       <button data-filter="6" onClick={this.handleType}>6</button> 
 
       <button data-filter="-" onClick ={this.handleAction} >-</button> 
 
      </div> 
 
      <div className="row"> 
 
       <button data-filter="1" onClick={this.handleType}>1</button> 
 
       <button data-filter="2" onClick={this.handleType}>2</button> 
 
       <button data-filter="3" onClick={this.handleType}>3</button> 
 
       <button data-filter="*" onClick ={this.handleAction} >*</button> 
 
       <button data-filter="/" onClick ={this.handleAction} >/</button> 
 
      </div> 
 
      <div className="row"> 
 
       <button data-filter="0" onClick={this.handleType}>0</button> 
 
       <button>save</button> 
 
       <button onClick={this.cancel}>cancel</button> 
 
       <button onClick={this.getResult}>=</button> 
 
      </div> 
 

 
     </div> 
 
    ); 
 
    } 
 
} 
 

 
ReactDOM.render(<Calculator/>, document.getElementById('app'))
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script> 
 
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script> 
 

 
<div id='app'>

+0

vielen Dank! – Polina