react-native 中promise使用

1.返回一个promise

getTheme(){
        return new Promise((resolve,reject)=>{
            AsyncStorage.getItem(Theme_key,(error,result)=>{

                if (error) {
                    
                    reject(error);
                    return;
                }

                if (!result) {
                    this.save(ThemeFlags.Default);
                    result = ThemeFlags.Default;
                }

                resolve(ThemeFactory.createTheme(result));

            })
        })
    }

2. 使用

 new ThemeDao().getTheme().then((data)=>{
            dispatch(onThemeChange(data))
        }).catch(e=>{
            console.log(e)
        })

loadData2(){

    let url = `https://api.github.com/search/repositories?q=${this.searchKey}`;
    fetch(url)
      .then(response => {

        console.log("response: " + response);
        if(response.ok){
          return response.text();
        }
        throw new Error ("服务没有响应");

      })
      .then(responseText => {
        this.setState({

          showText:responseText
        })
      })
    
      .catch(e => {
        alert(e.toString());
         this.setState({
          showText:e.toString
         })
      })

  }

3.使用async和await接收promise

export function onLoadLanguage(flagkey){
    return async dispatch =>{
    
        try{
            
            //这里返回的是一个promise
            let languages = await new LanguageDao(flagkey).fetch();
            dispatch({type:types.LANGUAGE_LOAD_SUCCESS,languages:languages,flag:flagkey})

        }catch(e){

        }
    }
}