how to call a method within a method in iphone - iphone

Question

i am facing problem when i call method within method of another class like this i have method for button when someone click on button
//within ViewController.m button method
-(IBAction)login:(id)sender
{
DBHelper *objdb = [[DBHelper alloc] init];
[objdb loginnow:textname.text andpassword:textpassword.text];
}
and this button method calling this method in DBhelper.m file and it succesfully calling this method
-(void) loginnow:(NSString *) username andpassword:(NSString *) password
{
[self createEditableCopyOfDatabaseIfNeeded];
[self initializeDatabase];
const char *sql;
NSString *querySQL = [NSString stringWithFormat: #"SELECT username, password FROM CONTACT WHERE username='%#' AND password='%#'",username,password];
sql = [querySQL UTF8String];
if (sqlite3_prepare_v2(database, sql, -1, &init_statement, NULL) != SQLITE_OK) {
NSAssert1(0, #"Error: failed to prepare statement with message '%s'.", sqlite3_errmsg(database));
}
while (sqlite3_step(init_statement) == SQLITE_ROW)
{
NSLog(#"char sql = %s" ,sql);
dbusername = [NSString stringWithUTF8String:(char *)sqlite3_column_text(init_statement,0)];
dbpassword = [NSString stringWithUTF8String:(char *)sqlite3_column_text(init_statement,1)];
}
if ([dbusername isEqualToString:username] && [dbpassword isEqualToString:password])
{
//DBHelper.callingViewController = self;
[self.callingViewController addview];
}
else if (dbusername != username || dbpassword != password)
{
NSLog(#"dbusername is = %#" ,dbusername);
NSLog(#"dbpassword is = %#" ,dbpassword);
UIAlertView *alert = [[UIAlertView alloc]
initWithTitle:#"Login Failed"
message:#"Username Or Password is not Correct"
delegate:nil
cancelButtonTitle:nil
otherButtonTitles:#"OK ", nil];
[alert show];
[alert release];
}
sqlite3_reset(init_statement);
[self closeDatabase];
}
and also in DBhelper.h i define property for this
#property (strong) ViewController * callingViewController;
and within if condidtion in lognow method if password and username is succesully match i am calling this mathod in Viewcontroller.com file but am fail to call that
//ViewController.m
-(void) addview
{
DBHelper *f = [[DBHelper alloc] init];
f.callingViewController = self;
newview.center = CGPointMake(1000, 1000);
}

Answer 1

Though it's not wise to hold the viewController in the DBhelper(it breaks MVC), you could call your ViewController's method as your code but remember to set to pass your ViewController to the DBhelper. Maybe like this:
//ViewController.m
-(IBAction)login:(id)sender
{
DBHelper *objdb = [[DBHelper alloc] init];
[objdb loginnow:textname.text andpassword:textpassword.text viewController:self];
}
//DBHelper.m
-(void) loginnow:(NSString *) username andpassword:(NSString *)password viewController:(ViewController *)vc
{ ...
if ([dbusername isEqualToString:username] && [dbpassword isEqualToString:password])
{
[vc addview];
}
...
}
But in fact you should use a delegate (or block or notification, but delegate is the most case) here. Like this:
In DBHelper.h, before #interface, add
#class DBHelper;
#protocol DBHelperDelegate <NSObject>
-(void) DBHelp:(DBHelper *)helper didFinishedLoginSuc:(BOOL)suc;
#end
and between the #interface and #end tag, add(suppose you are not using ARC)
#property (nonatomic, assign) id delegate;
in the DBHelper.m, in the #implementation, add(suppose you are not using auto synthesize)
#synthesize delegate = _delegate;
Now, you can change the [self.callingViewController addview]; to
if (self.delegate && [self.delegate responseToSelector:#selector(DBHelp:didFinishedLoginSuc:)]) {
[self.delegate DBHelp:self didFinishedLoginSuc:YES];
}
Now you get a delegate prepared for every view controller which obey the DBHelperDelegate.
In your ViewController.h, tell the compiler that it obey the DBHelperDelegate by add behind the class declare:
#interface ViewController:UIViewController<DBHelperDelegate>
and change the addView method name to
-(void) DBHelp:(DBHelper *)helper didFinishedLoginSuc:(BOOL)suc
At last, when you click the button, set self as the objdb's delegate
-(IBAction)login:(id)sender
{
DBHelper *objdb = [[DBHelper alloc] init];
objdb.delegate = self;
[objdb loginnow:textname.text andpassword:textpassword.text];
}
Now, when you login successfully, -(void) DBHelp:(DBHelper *)helper didFinishedLoginSuc:(BOOL)suc in ViewController.m will be called and you can deal with your view.
Remember to set the delegate to nil when your viewController gets dealloc, or you will expect an memory error. Be careful.