react本机sqllite值未显示

Question

this.getDetails()；

getDetails = () => {
let userDetails = [];
db.transaction((tx) => {
tx.executeSql('select * from users where role=?',['students'],(tx,results) => {
let details = []
if(results.rows.length > 0){
for(let i=0; i < results.rows.length; i++){
details.push(results.rows.item(i));
}
}
userDetails = details;
//Data is displayed  here
console.log(userDetails)
})
})
// Data is not printed here
console.log(userDetails) // []
}

在上面的代码片段中，我可以在tx.executeSql中获取数据(userDetails)，但不能在db.transaction块之外获取。

有人能帮助我如何在db.transaction块之外显示数据吗。

Answer 1

定义用于从DB获取userDetails的promise函数。

async dbAction = () => {
return new Promise((resolve, reject) => {
db.transaction((tx) => {
tx.executeSql('select * from users where role=?',['students'],(tx,results) => {
let details = []
if(results.rows.length > 0){
for(let i=0; i < results.rows.length; i++){
details.push(results.rows.item(i));
}
}
//Data is displayed  here
resolve(details);
})
})
});
}

然后你可以这样称呼它。

getDetails = () => {
let userDetails = [];
try {
let userDetails = await dbAction();
console.log(userDetails);
} catch (e) {
}
}