UILabel wont show the previous characters, only the last letter - ios

Question

Goal is to enumerate every character in the String. That is 'w' will appear then after 1 sec will be replaced by 'h' then 'e' then 'n'.
Problem my label only shows the last letter.
What i did:
1. drag a label and a button on the PlayViewController.
2. create the property for Label
3. create action for button
In my PlayViewController.h:
#import <UIKit/UIKit.h>
#interface PlayViewController : UIViewController
#property (strong, nonatomic) IBOutlet UILabel *listChar;
- (IBAction)startGame:(id)sender;
#end
In my PlayViewController.m:
#import "PlayViewController.h"
#interface PlayViewController ()
#end
#implementation PlayViewController
NSString *word;
NSTimer *myTimer;
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
self.listChar.text = #" ";
word = #"when";
}
- (IBAction)startGame:(id)sender {
myTimer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:#selector(listLetter:) userInfo:nil repeats:YES];
}
-(void) listLetter:(NSTimer*) myTimer {
for(int i=0; i<[word length]; i++){
unichar letter = [word characterAtIndex: i];
self.listChar.text = [NSString stringWithFormat:#"%C", letter];
}
}
#end

Answer 1

If you want to know about why this happning then refer #Nitin's answer, and if you want to solve in other way then just use following code
-(void) listLetter:(NSTimer*) myTimer
static int pos = 1;
self.listChar.text = [word substringToIndex:pos];
if (++pos > word.length) {
[myTimer invalidate];
}
}