Pulling User Information from Parse Database - ios

Question

I am using Parse as my backend for my app. Once the user logs into their account I am trying to get the next view to say "Welcome, (First Name)" at the top. However, I cannot seem to figure out how to accomplish this even using Parse's online documents. Their site directed me here for further assistance. I have tried using their query feature, but could not figure it out. In other words, I am trying to pull the current logged in user's first name, from the database and display it once logged in.
Current code:
PFQuery *query = [PFUser query];
[query whereKey:#"firstName" equalTo:currentUser]; // find user's first name
NSArray *firstName = [query findObjects];
Previous code:
PFUser *currentUser = [PFUser currentUser];
if (currentUser) {
// do stuff with the user
Welcome.text = [NSString stringWithFormat:#"Welcome,", currentUser];

Answer 1

Your overcomplicating things.
You don't have to execute a query every time the view loads, instead you should put this in a plist or NSUserDefaults as not to use an API request simply to display the current users name.
However, you can do the following to the current users username :
if ([PFUser currentUser]) {
Welcome.text = [NSString stringWithFormat:#"Welcome, %#", [PFUser currentUser].username];
}

Answer 2

First of all you should check if you actually sign-up and/or logged into Parse with this kind of function:
[PFUser signUpInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
}];
[PFUser logInWithUsernameInBackground:#"My username" password:#"My password" block:^(PFUser *validUser, NSError *error) {
}];
Check this link: https://parse.com/docs/ios_guide#users-signup/iOS
After you did this, whenever you you want to retrieve your user information,
[PFUser currentUser] is the right way to call some information:
Say for example you want to retrieve the objectId you can get it like this:
NSString *str = [PFUser currentUser].objectId;
Or say you want to set a custom value like this:
NSString *str = #"My custom object";
[PFUser setObject:str forKey:#"MyCustomObject"];
[PFUser saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
}];
Than you retrieve it like this:
NSString *str = [PFUser objectForKey:#"MyCustomObject"];
You should really check the documentation and example by Parse that are really well explained ! ;)
(Here are some tutorials/Examples by Parse: https://parse.com/tutorials)

Answer 3

How is the transition from your login to your main view set up? Are they both two different controllers?
If so, you should look into NSNotificationCenter...
In your MainViewController, implement
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(loadObjects)
name:#"loginFinished"
object:nil];
And loadObjects will be
- (void)loadObjects
{
Welcome.text = [NSString stringWithFormat:#"Welcome %#", [[PFUser currentUser] objectForKey:"userNameField"]];
}
* You need to parse the PFUser object to access its fields. Its just a dictionary so supply it a key 'username' or whatever, and you receive a value 'myusername'. *
Then in your LoginViewController, within your [PFUser logInWithUsernameInBackground:password:block
Implement this
[PFUser logInWithUsernameInBackground:#"My username" password:#"My password" block:^(PFUser *validUser, NSError *error) {
if (!error) {
[[NSNotificationCenter defaultCenter] postNotificationName:#"loginFinished" object:nil];
}
}];
But this is basically how you should setup your login->main flow. Learn NSNotifications, Delegation, and maybe KVO... Learning these will make you a understand how data can be passed around in the iOS/Mac environment.
Heres an analogy for all of them:
NSNotification: A teacher(NSNotification poster) announces a test to all his students(NSNotification observer), or at least the one's who are currently in class, students missing class aren't observing.
Delegate: A student finishes a test and informs the professor(delegate).
KVO: A student(KVO poster) completes a question and raises their hand where the teacher or even other students could be KVOs (key-value observers) and act on their action.