CODEWITHSUNDEEP
iphoneobjective-cios4
Zee
Zee

Reputation: 172

iPhone Application crashes

When I do the following my application crashes and I get an error (terminate called after throwing an instance of 'NSException') whenever i run the simulation:

for (...)
    [Array1 replaceObjectAtIndex:i withObject: [NSString stringWithFormat:@" Trip %i",i+1]]

OK after writing the problem I have found that the error is "0 is beyond bounds for empty array".

Upvotes: 0

Views: 137

Answers (3)

JeremyP
JeremyP

Reputation: 86651

You really really really need to post the type of exception and your code to give us a reasonable chance of solving your problem. However, I'm going to taker a shot at it anyway.

My guess is your code looks something like this:

Array1 = [[NSMutableArray alloc] initWithCapacity: someNumber];

for (i = 0 ; i < someNumber ; ++i)
{
    [Array1 replaceObjectAtIndex:i withObject: [NSString stringWithFormat:@" Trip %i",i+1]];
}

All arrays start out with 0 objects in them even if you use -initWithCapacity:. That method only provides a hint to the runtime that the array will grow to the specified size at some point. You need to use -addObject:.

Edit

Yep, from your edit, I'm sure I am right. The array has started out empty and you are trying to replace the object at index 0 which isn't there yet.

The code above should be changed as follows:

array1 = [[NSMutableArray alloc] initWithCapacity: someNumber]; // fixed naming convention too :-)

for (i = 0 ; i < someNumber ; ++i)
{
    [array1 addObject: [NSString stringWithFormat:@" Trip %i",i+1]];
}

-addObject: adds the new objects to the end of the array.

If you want something that looks more like a C or Java array, you can prefill the array with NSNull objects

array1 = [[NSMutableArray alloc] initWithCapacity: 6]; // fixed naming convention too :-)

for (i = 0 ; i < 6 ; ++i)
{
    [array1 addObject: [NSNull null]];
}

// Now the following will work
[array1 replaceObjectAtIndex: 4 withObject: @"foo"];

Upvotes: 2

Matt N.
Matt N.

Reputation: 1239

Ok, here is a guess (I can't do better without more information):

You cannot change an object you are iterating over.

(Bad) Example:

for (NSObject *obj in Array1){
    [Array1 replaceObjectAtIndex:i withObject: [NSString stringWithFormat:@" Trip %i",i+1]]
}

Upvotes: 1

Jhaliya - Praveen Sharma
Jhaliya - Praveen Sharma

Reputation: 31722

if you are using replaceObjectAtIndex method with NSArray array type object, there is possibility of getting exception (crashed).

Use NSMutableArray for managing a modifiable array of objects.

Although replaceObjectAtIndex can also be raised the following Exception for Object and Index

Index: Raises an NSRangeException if index is beyond the end of the array.

Object: Raises an NSInvalidArgumentException if Object you are passing is nil.

Upvotes: 1

Related Questions