local variables, NSArray, EXEC_BAD_ACCESS on initWithObjects

Question

I have some arrays that I only need in my .M file, so I thought that I declare them in the interface brackets like so in MyViewController.m ( by this I am making them private variables, in Java C# lingo)

   @interface MyViewController () {
    NSArray *myArray; 
   }
   @end

   @implementation FilterViewController
   - (void)viewDidLoad
   {
      [super viewDidLoad];
      // This line throws  an error
      myArray = [NSArray arrayWithObjects: @"1", @"2","3", @"4", nil];

Now the last line throws an EXEC_BAD_ACCESS, and I don;t know why?

I am new to Objective C coming from C#.Net, I think what I did with my declaration is like declaring private variables, if thats incorrect I am eager to know the correct way of doing it. Thanks.

Answer 1

Generally you would use properties for something like this, but with ARC it wont matter.

But the problem you have here is with "3" instead of @"3" . "3" is an array of characters, while the @ is a literal which turns the array into an NSString. Since NSArray can only store objects, it crashes when you try to add a char*

Answer 2

Note that a better way to create the array would be to use the new "container literals":

myArray = @[@"1", @"2", @"3", @"4"];

Then the compiler would give an error message if you accidentally omit the @ (or generally if any of the collection elements is not an Objective-C object), instead of your application crash at runtime.

Answer 3

You are missing this symbol @ in this line. So you need to use this one @"3" .

Answer 4

很简单，您在"3"之前错过了@符号。

Answer 5

myArray = [NSArray arrayWithObjects: @"1", @"2",@"3", @"4", nil];

Answer 6

Not a direct answer, but you don't need to declare your private iVars in an extension, you could just put it straight in the implementation: eg

@interface FilterViewController {
    NSArray *myArray; 
}

Although a better solution would be to use a property, which you do declare in the extension:

@interface FilterViewController () {
    @property (copy, nonatomic) NSArray *myArray; 
}
@end

@implementation FilterViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    self.myArray = @[@"1", @"2",@"3", @"4"];
}