我正在实施链式承诺，但一个函数无法执行基本上我有以下返回承诺的函数
1. open database
2. add record // incase record exists remove it
3. remove record called from no 2
这是我实施的方式
openDb(): Promise<boolean> { //opens database
return new Promise((resolve, reject) => {
this.sqlite.create({
name: this.dbname,
location: this.dblocation
})
.then((db: SQLiteObject) => {
this.database = db;
resolve(true)
})
.catch(e => reject(e.message));
});
}
然后添加记录
add(item: string, value: any): Promise<boolean> {
return new Promise((resolve, reject) => {
this.openDb()
.then(() => {
this.database.transaction(
(tx: any) => {
tx.executeSql(`
CREATE TABLE IF NOT EXISTS '${tbl_name}'
(item_id INTEGER PRIMARY KEY AUTOINCREMENT, item unique, value)` ); //incase tbl not there
this.remove(item) //next function which gets executed
.then(() => {
///THIS PART IS NEVER EXECUTED
tx.executeSql(`
INSERT INTO '${tbl_name}' (item, value) VALUES(?, ?)`, [item, value],
(t: any, results: any) => {
console.log("executed successifully");
resolve(true)
},
(t: any, message: any) => {
console.log("Failed to execute");
reject(false)
})
})
.catch(reject(false))
}
);
})
.catch(e => reject(e.essage));
});
}
删除项目功能
remove(item: string): Promise<boolean> {
return new Promise((resolve, reject) => {
this.openDb()
.then(() => {
this.database.transaction(
(tx: any) => {
tx.executeSql(`
DELETE FROM '${tbl_name}' WHERE item ='${item}'
`, [],
(t: any, results: any) => {
console.log("executed successifully");
resolve(true)
},
(t: any, message: any) => {
console.log("Failed to execute");
reject(false)
})
}
);
})
.catch(e => reject(e.essage));
});
}
删除项目成功执行，但添加块从未执行过，抛出错误
InvalidStateError: DOM Exception 11: This transaction is already finalized.
Transactions are committed after its success or failure handlers are called.
If you are using a Promise to handle callbacks, be aware that implementations
following the A+ standard adhere to run-to-completion semantics
and so Promise resolution occurs on a subsequent tick and therefore
after the transaction commits
有什么问题？