print reverse of a string - iphone

Question

I am writing a program which prints the reverse of a string in a textfield, taking input text from the other textfield. When I press enter after entering text into one textfield the result(reverse) should be dispalyed in the other text field.
I have tried like this, but am getting weird results.
.h file:
#import <UIKit/UIKit.h>
#interface reverseVC : UIViewController {
UITextField *textEntered;
UITextField *textDisplay;
}
#property (nonatomic,retain) IBOutlet UITextField *textDisplay;
#property (nonatomic,retain) IBOutlet UITextField *textEntered;
- (NSMutableArray*) stringReverse;
- (IBAction) enter;
#end
.m file
- (NSMutableArray *) stringReverse
{
NSString *value = textEntered.text;
NSArray *tempArray = [[[NSArray alloc] initWithObjects:value,nil] autorelease];
NSMutableArray *arr = [[[NSMutableArray alloc] init] autorelease];
for (int i=[tempArray count]-1; i>=0; i--)
{
[arr addObject:[tempArray objectAtIndex:i]];
NSLog(#"the object is:%c",arr);
}
return arr;
}
-(IBAction)enter
{
textDisplay.text = [NSString stringWithFormat:#"%c",[self stringReverse]];
}
Earlier got warnings like SIG_ABT and EXE_BAD_ACCESS before placing nil and autorelease in array initialisations. Now the warnings are solved but results undesiredly.
Where am I going wrong?

Answer 1

You insert the NSString object in your array. Its count is 1. You have to go from the end of the string to the beginning and append the character to a new string. You ca do it like this:
-(NSString*)reverseString:(NSString*)string {
NSMutableString *reversedString;
int length = [string length];
reversedString = [NSMutableString stringWithCapacity:length];
while (length--) {
[reversedString appendFormat:#"%C", [string characterAtIndex:length]];
}
return reversedString;
}

Answer 2

Another way to reverse strings is to use the reverse string enumerator.
- (NSString *)reverseString:(NSString *)string {
NSMutableString *reversedString = [[NSMutableString alloc] init];
NSRange fullRange = [string rangeOfString:string];
NSStringEnumerationOptions enumerationOptions = (NSStringEnumerationReverse | NSStringEnumerationByComposedCharacterSequences);
[string enumerateSubstringsInRange:fullRange options:enumerationOptions usingBlock:^(NSString *substring, NSRange substringRange, NSRange enclosingRange, BOOL *stop) {
[reversedString appendString:substring];
}];
return reversedString;
}

Answer 3

use this
NSString *str=textEntered.text;//
NSMutableArray *temp=[[NSMutableArray alloc] init];
for(int i=0;i<[str length];i++)
{
[temp addObject:[NSString stringWithFormat:#"%c",[str characterAtIndex:i]]];
}
temp = [NSMutableArray arrayWithArray:[[temp reverseObjectEnumerator] allObjects]];
NSString *reverseString=#"";
for(int i=0;i<[temp count];i++)
{
reverseString=[NSString stringWithFormat:#"%#%#",reverseString,[temp objectAtIndex:i]];
}
NSLog(#"%#",reverseString);

Answer 4

I revers my strings with a few lines of code. Rather late, but just putting it out there :)
- (NSString*) reverseMyString:(NSString*)theString
{
NSString *final = #"";
for(int i = theString.length-1; i>=0; i--)
final = [NSString stringWithFormat:#"%#%c", final, [theString characterAtIndex:i]];
return final;
}

Answer 5

NSString *str = #"hello";
int length = [str length];
NSLog(#"%d",length);
NSMutableString *rev = [[NSMutableString alloc] initWithCapacity:[str length]];
while (length > 0) {
--length;
[rev appendString:[NSString stringWithFormat:#"%c", [str characterAtIndex:length]]];
}
NSLog(#"%#", rev);

Answer 6

Using characterAtIndex doesn't work well with non-ascii characters.
- (NSString *)reverseMyString:(NSString *)string {
NSString *output = [[NSString alloc] init];
for(int i = string.length-1; i>=0; i--) {
output = [output stringByAppendingString:[string substringWithRange:NSMakeRange(i, 1)]];
}
return output;
}