Retain-Release in Objective-C

Question

I am new to Objective-C and I am confused about this retain-release thing. Are parameters retained automatically? Do I need to release them?

Here is my code. Did I do the retain-release thing (and everything else) correctly?

#import "ACStringTokenizer.h"


@implementation ACStringTokenizer

- (id)init
{
    self = [super init];
    if (self) {
        // Initialization code here.
    }

    return self;
}

- (id)initWithStr:(NSString *)theString
{
    self = [super init];
    if (self) {
        string = [theString retain];
        delimiters = @" ";
        doesReturnDelims = NO;
    }

    return self;
}

- (id)initWithStr:(NSString *)theString andDelims:(NSString *)theDelimiters
{
    self = [super init];
    if (self) {
        string = [theString retain];
        delimiters = [theDelimiters retain];
        doesReturnDelims = NO;
    }

    return self;
}

- (id)initWithStr:(NSString *)theString andDelims:(NSString *)theDelimiters andDoesReturnDelims:(BOOL)returnDelims
{
    self = [super init];
    if (self) {
        string = [theString retain];
        delimiters = [theDelimiters retain];
        doesReturnDelims = returnDelims;
    }

    return self;
}

- (int)countTokens
{
    return numberOfTokens;
}

- (BOOL)hasMoreTokens
{
    return ![queue isEmpty];
}

- (NSString *)nextToken
{
    return [queue remove];
}

- (void)dealloc
{
    [string release];
    [delimiters release];
    [queue release];

    [super dealloc];
}

@end

Thanks in advance.

P.S. How do I make init with no parameters invalid?

Answer 1

This might be better suited to http://codereview.stackexchange.com?

Anyway, a few points:

• You should read up on the concept of Designated Initializer. In your case you'd probably make initWithStr:andDelims:andDoesReturnDelims: the designated initializer. Only this initializer may call [super init]. All other initializers call [self initWithStr:andDelims:andDoesReturnDelims:] instead of [super init].

• There are some more elaborate ways to make init invalid, but if you want to disable it I'd simply make it return nil. However, I don't really see a reason why you'd want to do this in this particular case.

• The retains in your init methods and the dealloc method seem to be alright. Method parameters are valid until the end of the method, if you want to keep them beyond that, e.g. in instance variables, you need to retain them (which you seem to have done correctly).

However, there's a whole lot of code omitted in your example so obviously I'm only commenting on what you've posted.