Hold off until the commitments have been fulfilled before determining if they are true or false

Question

Hold off until the commitments have been fulfilled before determining if they are true or false

I need assistance with waiting for a promise to return within a method.

public async loginOffline(username: string, password: string) {
    const data = await this.database.getItem('currentUser', 'login');
    this.userLogin = data;
    console.log(`${username} ${this.userLogin.username} ${password} ${this.userLogin.password}`);
    if (username === this.userLogin.username && password === this.userLogin.password) {
        return true;
    } else {
        return false;
    }
}

/********* Calling the method and deciding what to do **************/
if (await loginOffline('myname', 'mypassword')) {
    // Do something.....
} else {
    // Do something else .....
}
......

The current implementation is not functioning as expected. The caller of the loginOffline method only needs confirmation on whether the login was successful. I have attempted multiple approaches but none have worked so far.

If anyone can provide some guidance, it would be greatly appreciated. Thank you very much.

javascript angular typescript

Answer 1

Answer №1

To continue the promise chain, simply use another then method. Implement it like this:

loginOffline('myname', 'mypassword').then(result =>{
   if(result){
     //perform a specific action
   }else{
     //perform a different action
   }
})

For additional information on promise chaining

Answer 2

To continue the promise chain, simply use another then method. Implement it like this:

loginOffline('myname', 'mypassword').then(result =>{
   if(result){
     //perform a specific action
   }else{
     //perform a different action
   }
})

For additional information on promise chaining

Answer 3

Answer №2

Here is an example of using the Promise object:

function checkCredentials(username: string, password: string) {
  return database.fetchUser('currentUser').then(userData => {
      let user = userData;
      console.log(username + ' ' + user.username + ' ' + password + ' ' + user.password );
      if (username === user.username && password === user.password) {
        return true;
      } else {
        return false;
      }
    }).catch(err => {
      return false;
    });   
}

checkCredentials('myname', 'mypassword').then((result) => {
    if(result) {
      // Credentials are correct
    } else {
      // Incorrect credentials
    }
 })

Answer 4

Here is an example of using the Promise object:

function checkCredentials(username: string, password: string) {
  return database.fetchUser('currentUser').then(userData => {
      let user = userData;
      console.log(username + ' ' + user.username + ' ' + password + ' ' + user.password );
      if (username === user.username && password === user.password) {
        return true;
      } else {
        return false;
      }
    }).catch(err => {
      return false;
    });   
}

checkCredentials('myname', 'mypassword').then((result) => {
    if(result) {
      // Credentials are correct
    } else {
      // Incorrect credentials
    }
 })

Answer 5

Answer №3

Suraj's response provides the correct solution - simply wrap another .then() around the returned result. Alternatively, you can utilize the await/async keywords to refactor the code.

 public async loginOffline(username: string, password: string) {
    try {
      this.userLogin = await this.database.getItem('currentUser', 'login');
    } catch(e) {
      return false;
    }
    console.log(username + ' ' + this.userLogin.username + ' ' + password + ' ' + this.userLogin.password );
    return (
      username === this.userLogin.username &&
      password === this.userLogin.password);
  }

// This code must also be inside a function marked as 'async':
/********* call the method and descide what to do **************/
if(await loginOffline('myname', 'mypassword'){
// Do something.....
} else {
// Do something else .....
}
......

It is important to note that every async function will automatically convert its return value into a Promise, requiring async to be used throughout the entire call stack. If making the caller async is not an option, you can still use then on the result:

// If the caller cannot be marked `async`:
/********* call the method and descide what to do **************/
loginOffline('myname', 'mypassword').then(result => {
  if (result) {
  // Do something.....
  } else {
  // Do something else .....
  }
});
......

Answer 6

Suraj's response provides the correct solution - simply wrap another .then() around the returned result. Alternatively, you can utilize the await/async keywords to refactor the code.

 public async loginOffline(username: string, password: string) {
    try {
      this.userLogin = await this.database.getItem('currentUser', 'login');
    } catch(e) {
      return false;
    }
    console.log(username + ' ' + this.userLogin.username + ' ' + password + ' ' + this.userLogin.password );
    return (
      username === this.userLogin.username &&
      password === this.userLogin.password);
  }

// This code must also be inside a function marked as 'async':
/********* call the method and descide what to do **************/
if(await loginOffline('myname', 'mypassword'){
// Do something.....
} else {
// Do something else .....
}
......

It is important to note that every async function will automatically convert its return value into a Promise, requiring async to be used throughout the entire call stack. If making the caller async is not an option, you can still use then on the result:

// If the caller cannot be marked `async`:
/********* call the method and descide what to do **************/
loginOffline('myname', 'mypassword').then(result => {
  if (result) {
  // Do something.....
  } else {
  // Do something else .....
  }
});
......

Answer 7

Answer №4

For the solution, please refer to the code snippet below:

const checkUserPermission = () => {
  return new Promise((resolve, reject) => {
    fetchData().then((data) => {
      if (data) {
        resolve(true);
      } else {
        resolve(false);
      }
    }).catch((error) => {
      resolve(false);
    })
  })
}

function fetchData() {
  return new Promise((resolve, reject) => { 
    setTimeout(() => {
      resolve("Data");
    }, 100)
  })
}

checkUserPermission().then((data) => {
  alert(data);
});

Answer 8

For the solution, please refer to the code snippet below:

const checkUserPermission = () => {
  return new Promise((resolve, reject) => {
    fetchData().then((data) => {
      if (data) {
        resolve(true);
      } else {
        resolve(false);
      }
    }).catch((error) => {
      resolve(false);
    })
  })
}

function fetchData() {
  return new Promise((resolve, reject) => { 
    setTimeout(() => {
      resolve("Data");
    }, 100)
  })
}

checkUserPermission().then((data) => {
  alert(data);
});

Hold off until the commitments have been fulfilled before determining if they are true or false

Answer №1

Answer №2

Answer №3

Answer №4

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