Gheryd: 2018

In these example form components are react uncontrolled components.

It's best practice using controlled input (value+onChange. https://reactjs.org/docs/forms.html)

Example 1: implement componentDidUpdate method



class Form extends Component {

    submit = (e) => {
        e.preventDefault();
        var user = Object.keys(this.refs).reduce( (obj, k) =>{
            obj[k] = this.refs[k].value;
            this.refs[k].value = '';
            return obj;
        }, {} );
        this.props.onSubmit(user);
    }

    onChange = ({target:el}) => el.value = el.value.toUpperCase();

    render() {
        return (
        <form onSubmit={this.submit}>
            <div className="form-group">
                <input type="text" 
                       ref="name"
                       className="form-control" 
                       placeholder = "name"/>
            </div>
            <div className="form-group">
                <input type="text" 
                       ref="surname" 
                       onChange={this.onChange} 
                       className="form-control" 
                       placeholder="surname" />
            </div>
            <button type="submit" className="btn btn-primary">add</button>
        </form>
        );
    }

    componentDidUpdate(){
        const {user} = this.props; 
        this.refs.name.value = user.name;
        this.refs.surname.value = user.surname; 
    }
}

Example 2: use defaultValue



class Content6 extends Component {
    state = { 
        formCfg: {name:'', cities:[]},
        submittedData: {}
     }

    dataList = [
        {name:'Pippo', cities:['Milan', 'Rome', 'Palermo'], isMale:true, defaultCity:'Rome' },
        {name:'Tina', cities:['Torino', 'Genova', 'Pavia'], isMale:false},
        {name:'Pino', cities:['Venice', 'Padova', 'Firenze'], isMale:true}
    ]

    onClick = (formCfg) => this.setState({formCfg}); 
    onSave = (submittedData) => this.setState({submittedData});
    render() {
        const {formCfg, submittedData} = this.state; 
        return ( <div>
            <p>click item to fill form:</p>
            {this.dataList.map( (cfg, i)=>(
            <div key={i} onClick={(ev)=>this.onClick(cfg)} 
                style={{cursor:'pointer', backgroundColor:'#CCC', margin:2}}>
                {JSON.stringify(cfg)}
            </div>))}
            <div>
                <p>Submitted data: {JSON.stringify(submittedData)}</p>
            </div>
            <div><FormSL {...formCfg} save={this.onSave}/></div>

        </div> );
    }
}

//stateless component
class FormSL extends Component {

    onSubmit = ({name: {value:name}, city:{value:city},isMale:{checked:isMale}}) => 
                   this.props.save({name, city, isMale});

    render() { 
        const {name, cities,isMale, defaultCity} = this.props;
        return ( <form>
            <input ref='name' defaultValue={name} type="text" className="form-control" /><br/>
            <select ref='city' name="" id="" className="form-control" size={cities.length+1}>
                <option value=''>[select city]</option>
                {cities.map((city)=><option 
                    key={city} 
                    value={city.toUpperCase()} 
                    selected={defaultCity===city}>
                    {city}
                </option> ) }
            </select><br/>
            <input ref="isMale" type="checkbox" defaultChecked={isMale} /> isMale<br/>
            <button type="button" onClick={() => this.onSubmit(this.refs)} >submit</button>
        </form> );
    }
}

Gheryd

3 agosto 2018

React prefill input/form