Question

我有这个函数，我在typescript和nativescript中写入count的值从sqlite返回为promise但不可访问因此函数总是返回false

checkIfBookmarkAlreadyExist(study_number:string){
        this.countInDb=0;
        (new Sqlite("sts.db")).then(db => {
         this.countInDb=db.get("SELECT count(*) FROM bookmarks WHERE study_number= ?",[study_number] ).then(row => {


            return row;

         });
        });
        console.log("value of countInDb ouside: ", this.countInDb); 
        if(this.countInDb>1){
            return true
        }else{
            return false;
        }

    }

Answer 1

也许你可以试试：

让它'NESTED'功能：

checkIfBookmarkAlreadyExist(study_number:string){
    this.countInDb=0;
    let flag = true;//I don't recommend to make this variable global
    (new Sqlite("sts.db")).then(db => {
        db.get("SELECT count(*) FROM bookmarks WHERE study_number= ?",[study_number] )
            .then(row => {
                this.countInDb= row;
                console.log("value of countInDb ouside: ", this.countInDb); 
                if(this.countInDb>1){
                    return true
                } else{
                    return false;
                }
            });
        });  
}

尝试异步

if(checkIfBookmarkAlreadyExist(study_number)>1){
                return true
            }else{
                return false;
            }

async function checkIfBookmarkAlreadyExist(study_number:string) {     
    this.countInDb = 0;
    try {
        this.countInDb = await getData(study_number);
        console.log("value of countInDb ouside: ", this.countInDb); 
    } catch (e) {
        console.error(e);

    }
   return this.countInDb;
}

function getData(study_number:string) {
     (new Sqlite("sts.db")).then(db => {
         this.countInDb=db.get("SELECT count(*) FROM bookmarks WHERE study_number= ?",[study_number] )
            .then(row => {
                return row;
            });
        });
}

我想访问从nativescript sqlite返回的值

1 个答案: