how to fetch data from NSMutableArray ObjectAtIndex from integer value? [closed] - iphone

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I want to fetch data from my NSMutableArray, I am doing this
-(void)ViewDidLoad{
A_array = [[NSMutableArray alloc] init];
A_array = [NSMutableArray arrayWithObjects:#"4",#"6",#"2",#"3",#"0",#"5",#"1",#"2",#"4",#"1",#"0",#"2",#"4",#"2",#"0",#"3",nil]
var_Count_Answer_A = 0; // int
}
-(void)method_Second {
NSLog(#"%#",[A_array objectAtIndex:var_Count_Answer_A]); // This line is crashing if I click button again. First time line works fine but if we click button again and var_Count_Answer = 2 then it will crash.
NSString *str1 = [[NSString alloc]initWithFormat:#"%#",[A_array objectAtIndex:var_Count_Answer_A]]; // If I comment on NSLOG then this line will crash
A = [str1 integerValue];
NSLog(#"A is %d",A);
var_Count_Answer_A ++;
}
if I try this NSLog(#"%#",[A_array objectAtIndex:5]); // works fine
NSLog(#"%#",[A_array objectAtIndex:var_Count_Answer_A]); // var_Count_Answer_A =5; and crash
Any Idea or Suggestions would be highly appreciated.

Answer 1

Your code hurt my eyes
There are certain coding standards to be followed while writing code in Objective-C. Every language got one. They make code readable and understandable. You can refer to Cocoa Coding Guidelines and help yourself writing better looking code.
Explain Properly
Without the error message before crash no one can help you. Next time when you post about a crash, also explain the error message you got.
Was it a EXEC_BAD_ACCESS? If so it is the awesome garbage collector sweeping your array object away. Anyway your code sores my eyes and I am taking the privilege refactoring the code. Maybe it will help you.
A little bit of refactoring
NSArray *aArray;
- (void)viewDidLoad
{
[super viewDidLoad];
aArray = #[#"1", #"2", #"3", #"4"];
// or use[[NSArray alloc]initWithObjects:#"1", #"2", #"3", #"4", #"5"];
//Why do you need a mutable array while initializing it static?
}
- (void)methodSecond
{
static int counter = 0;
if (aArray) {
if (counter<aArray.count) {
NSLog(#"A is %u",[[aArray objectAtIndex:counter++]integerValue]);
} else {
counter = 0;
[self methodSecond];
}
}
}
Understand what you are doing
So a detail explanation of what I guess your problem is:
You're using [NSArray initWithObjects:] this creates an autoreleased object, and we got no control over its life time. And they get released if they are not referenced immediately after creating, which is probably whats happening your case. In my experience, mutable autoreleased object always sources bad access problems. So it is better to have the object alloc and inited, ie.. [[NSArray alloc]initWithObjects:] and I observe you are not adding/removing array members in run-time. There is no purpose of having a MutableArray.
In your code, you're creating two objects. The first array object is allocated and immediately dereferenced in the next line. Which is probably a mistake.
If you want to know more about auto-released objects. Read this.

Answer 2

Use
A_array = [[NSMutableArray alloc] initWithObjects:#"4",#"6",#"2",#"3",#"0",#"5",#"1",#"2",#"4",#"1",#"0",#"2",#"4",#"2",#"0",#"3",nil];
Instead you used.
A_array = [[NSMutableArray alloc] init];
A_array = [NSMutableArray arrayWithObjects:#"4",#"6",#"2",#"3",#"0",#"5",#"1",#"2",#"4",#"1",#"0",#"2",#"4",#"2",#"0",#"3",nil];
As I review Your Project is ARC disable try this Working fine for me.
ViewControler.h
#interface MasterViewController : UIViewController
{
NSMutableArray *A_array;
int var_Count_Answer_A;
}
ViewControler.m
-(void)viewDidLoad {
[super viewDidLoad];
A_array = [[NSMutableArray alloc] initWithObjects:#"4",#"6",#"2",#"3",#"0",#"5",#"1",#"2",#"4",#"1",#"0",#"2",#"4",#"2",#"0",#"3",nil];
var_Count_Answer_A = 0;
var_Count_Answer_A = 0; // int
}
-(IBAction)method_Second:(id)sender {
NSLog(#"%#",[A_array objectAtIndex:var_Count_Answer_A]);
NSString *str1 = [[NSString alloc]initWithFormat:#"%#",[A_array objectAtIndex:var_Count_Answer_A]]; // If I comment on NSLOG then this line will crash
int A = [str1 integerValue];
NSLog(#"A is %d",A);
var_Count_Answer_A++;
}
But As Everyone know at last there must be occur this exception.
NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 16 beyond bounds [0 .. 15]'
As trying to access array index object that does not exist.
And if you still have some error then First Enable NSZombie in your project Follow this.
-> "Product" menu, select "Edit Scheme", go to the "YourAp.app" stage in the left panel, and the "Arguments" tab on the right. You can then add NSZombieEnabled to the "Environment Variables" section and set the value to YES.
And Now Share your Crash Log.

Answer 3

in your code you are usimng two different varaibles once check thosetwo.
var_Count_Answer and var_Count_Answer_A

Answer 4

This error occurs because you are using an auto-released object.
When you call like:
A_array = [NSMutableArray arrayWithObjects:#"4",#"6",#"2",#"3",#"0",#"5",#"1",#"2",#"4",#"1",#"0",#"2",#"4",#"2",#"0",#"3",nil]
The A_array is an autoreleased object, you can't say when it'll be released. That is why this error occurs.
Solution:
Declare a property for the array like:
#property (nonatomic, strong) NSMutableArray *A_array;
Then modify your methods like:
-(void)ViewDidLoad
{
_A_array = [NSMutableArray arrayWithObjects:#"4",#"6",#"2",#"3",#"0",#"5",#"1",#"2",#"4",#"1",#"0",#"2",#"4",#"2",#"0",#"3",nil]
var_Count_Answer_A = 0; // int
}
-(void)method_Second
{
NSLog(#"%#",[_A_array objectAtIndex:var_Count_Answer_A])
NSString *str1 = [[NSString alloc]initWithFormat:#"%#",[_A_array objectAtIndex:var_Count_Answer_A]];
A = [str1 integerValue];
NSLog(#"A is %d",A);
var_Count_Answer_A ++;
}