Question

I have an object defined like this:
Scores.h:

@interface Scores : NSObject {
NSString *sentenceKey;
    NSMutableArray *scorrectAnswers;
}
@property (nonatomic, copy) NSString *sentenceKey;
@property (nonatomic, copy) NSMutableArray *scorrectAnswers;
+ (id)addScore:(NSString *)senKey;

- (id)initWithSentenceKey:(NSString *)sKey  
    scorrectAnswers:(NSMutableArray *)scorrectAs;

- (id)initWithSentenceKey:(NSString *)sKey;
- (void)removeArrayObjects;

Score.m:

#import "Scores.h"
@implementation Scores

@synthesize sentenceKey, scorrectAnswers;

+ (id)addScore:(NSString *)senKey
{
Scores *newScore = [[self alloc] initWithSentenceKey:senKey
                    scorrectAnswers:[NSMutableArray new]];
return [newScore autorelease];}

I’m trying to removeAllObjects on my mutable array with this method:

- (void)removeArrayObjects;{
   [scorrectAnswers removeAllObjects];}

…which I call from another program like this:

for (Scores *sScore in scores)
{   
    [sScore removeArrayObjects];
}

… and I get this error when I run it:

-[__NSArrayI removeAllObjects]: unrecognized selector sent to instance 0x53412d0

Can anyone tell me what I’m doing wrong here? Thanks.

Answer 1

You are not dealing with an NSMutableArray as the error indicates you have an immutable NSArray.

This question may be your answer NSMutableArray addObject: -[__NSArrayI addObject:]: unrecognized selector sent to instance

Basically the copy you used when defining your @property will cause the setter to be generated using

scorrectAnswers = [newMutableArray copy];

which returns an immutable NSArray.

You can re-implement this method and change the previous line for:

scorrectAnswers = [newMutableArray mutableCopy];

or use retain instead of copy

This can also occur when getting data from a plist

If you are using a plist it will return an NSArray even if you save an NSMutableArray it will be cast. So when retrieving you will need to do something like:

scorrectAnswers = [[NSMutableArray alloc] initWithArray:[userDefault objectForKey:@"my_array_key"]]