約束がエラー

Question

を投げる私は、次のエラーが発生します：私は約束を返すメソッドを呼び出していますというクラスを宣言した

{"__zone_symbol__currentTask":{"type":"microTask","state":"notScheduled","source":"Promise.then","zone":"angular","cancelFn":null,"runCount":0}}

どこ....ここ

export class TechPRODAO { 
sqlite: any; 
db: SQLiteObject; 

constructor() { 
    this.sqlite = new SQLiteMock(); 

    this.sqlite.create({ 
     name: 'techpro.db', 
     location: 'default' 
    }).then((_db: SQLiteObject) => { 
     this.db = _db; 
    }); 
}; 

public executeSql(sqlstatement: string, parameters: any): Promise<any> { 

    return this.db.executeSql(sqlstatement, parameters); 
} 

です私は、コール

export class AppointmentDAO { 
techprodao: TechPRODAO; 

constructor(_techprodao: TechPRODAO) { 
    this.techprodao = _techprodao; 
}; 

public insertAppointment(appointment: Appointment) { 
    console.log("insertAppointment called"); 
    this.techprodao.executeSql("INSERT INTO appointment (ticketnumber, customername, contactemail, contactphone, status, location, paymenttype, description, hascontract) " + 
     "VALUES(?, ?, ?, ?, ?, ?, ?, ?, ?)", [appointment.ticketnumber, appointment.customername, appointment.contactemail, appointment.contactphone, appointment.status, 
      appointment.location, appointment.paymenttype, appointment.description, appointment.hascontract]) 
     .then((data) => { 
      console.log("Inserted into appointment: ticketnumber=" + appointment.ticketnumber); 
     }, (error) => { 
      console.log("ERROR in insertAppointment: " + JSON.stringify(error)); 
     }); 
} 

insertAppointmentはは、ExecuteSQLにエラーがスローされますが、それは当たっていない理由を私は理解していないを作ります"then"を適切に。

Answer 1

一般的に、非同期のものをコンストラクタに入れないでください。彼らはいつ準備ができているのか分かりません。代わりに：

export class TechPRODAO { 
    sqlite: any; 
    db: Promise<SQLiteObject>; 

    constructor() { 
    this.sqlite = new SQLiteMock(); 

    this.db = this.sqlite.create({ 
     name: 'techpro.db', 
     location: 'default' 
    }); 
    } 

    public executeSql(sqlstatement: string, parameters: any): Promise<any> { 
    return this.db.then(db => executeSql(sqlstatement, parameters)); 
    } 
}