Question

If I create a property of type NSString without allocating space to it and assign some value to it , it works. Where as I do the same thing for a UITextField it doesn’t..? I am creating a textfield programmatically…. any help is appreciated.

EDIT:

I have created two properties in .h of SecondViewController…

@property (nonatomic,retain) NSString *text;
@property (nonatomic, retain) UITextField *textField;

Now if I create a new object secondViewController and say do this…

   secondViewController.text=@"Second View Controller";

this value is retained even though I did not alloc Memory to it…

and if i try to do the same thing for a textfield object this does not happen unless I allocate memory to it..

here is my SecondViewController…

//
//  SecondViewController.m
//  Tester
//
//  Created by Ankit on 4/16/12.
//  Copyright (c) 2012 __MyCompanyName__. All rights reserved.
//

#import "SecondViewController.h"

@implementation SecondViewController
@synthesize  text,textField;

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)didReceiveMemoryWarning
{
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Release any cached data, images, etc that aren't in use.
}

#pragma mark - View lifecycle

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSLog(@"The text is %@",text);

//   textField = [[UITextField alloc] initWithFrame:CGRectMake(10, 200, 300, 40)]; (if I `uncomment this than only this textField is visible)`
    textField.frame=CGRectMake(10, 200, 300, 40);
    textField.borderStyle = UITextBorderStyleRoundedRect;
    textField.font = [UIFont systemFontOfSize:15];
    textField.placeholder = @"enter text";
    textField.autocorrectionType = UITextAutocorrectionTypeNo;
    textField.keyboardType = UIKeyboardTypeDefault;
    textField.returnKeyType = UIReturnKeyDone;
    textField.clearButtonMode = UITextFieldViewModeWhileEditing;
    textField.contentVerticalAlignment = UIControlContentVerticalAlignmentCenter;    
    [self.view addSubview:textField];

//    textfield=[[UITextField alloc] init];
//    textfield.frame=CGRectMake(10,10,60, 30);
//    [self.view addSubview:textfield];
    // Do any additional setup after loading the view from its nib.
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    self.text=nil;
    self.textField=nil;
    NSLog(@"viewDidUnLoad");
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}
-(void)dealloc{
    NSLog(@"dealloc");
    [text release];
    [textField release];
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    // Return YES for supported orientations
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

@end

Answer 1

A property is just a reference to an object and the ‘space’ has to come from somewhere else. The only real difference with NSString is that the space is often in the form of a literal so you don’t see the allocation directly. @”Hello” is a real object that you can reference but in other cases you use [[NSString alloc] init…] constructions that are the same as [[UITextField alloc] init…] constructions.