How to replace an object in an NSMutableArray at a given index with a new object
- by shakeelw
Hi guys.
I have an NSMutableArray object(retained, synthesized as all) that is initiated just fine and I can easily add objects to it using the 'addObject:' method. But if I want to replace an object at a certain index with a new one in that NSMutableArray, it doesn't work.
For example:
ClassA.h
@interface ClassA : NSObject {
NSMutableArray *list;
}
@property (nonatomic, copy, readwrite) NSMutableArray *list;
end
ClassA.m
import "ClassA.h"
@implementation ClassA
@synthesize list;
(id)init
{
[super init];
NSMutableArray *localList = [[NSMutableArray alloc] init];
self.list = localList;
[localList release];
//Add initial data
[list addObject:@"Hello "];
[list addObject:@"World"];
}
// Custom set accessor to ensure the new list is mutable
(void)setList:(NSMutableArray *)newList
{
if (list != newList)
{
[list release];
list = [newList mutableCopy];
}
}
-(void)updateTitle:(NSString *)newTitle:(NSString *)theIndex
{
int i = [theIndex intValue]-1;
[self.list replaceObjectAtIndex:i withObject:newTitle];
NSLog((NSString *)[self.list objectAtIndex:i]); // gives the correct output
}
However, the change remains true only inside the method. from any other method, the
NSLog((NSString *)[self.list objectAtIndex:i]);
gives the same old value.
How can I actually get the old object replaced with the new one at a specific index so that the change can be noticed from within any other method as well.
I even modified the method like this, but the result is the same:
-(void)updateTitle:(NSString *)newTitle:(NSString *)theIndex
{
int i = [theIndex intValue]-1;
NSMutableArray *localList = [[NSMutableArray alloc] init];
localList = [localList mutableCopy];
for(int j = 0; j < [list count]; j++)
{
if(j == i)
{
[localList addObject:newTitle];
NSLog(@"j == 1");
NSLog([NSString stringWithFormat:@"%d", j]);
}
else
{
[localList addObject:(NSString *)[self.list objectAtIndex:j]];
}
}
[self.list release];
//self.list = [localList mutableCopy];
[self setList:localList];
[localList release];
}
Please help out guys :)
