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iOS Build a Blog Reader iPhone App Data Modeling Using a Custom Class

Posted by gregdodd
gregdodd
8,124 Points

Designated initializers

So first we created the - (id) initWithTitle:(NSString *)title; to set our title with each new Blog Post class. Does adding the + (id) blogPostWithTitle: (NSString *)title; not replace this now, or am I missing something.

Thanks

4 Answers

Stone Preston
Stone Preston
42,016 Points
Stone Preston
Stone Preston
42,016 Points

initWithTitle is an initializer, whereas blogPostWithTitle is a convenience constructor. You can use either one, although using a convenience constructor is easier since you dont have to call alloc first. 

 [[BlogPost alloc] initWithTitle:@"Some title"];

 [BlogPost blogPostWithTitle:@"some title"];
gregdodd
gregdodd
8,124 Points
gregdodd
gregdodd
8,124 Points

So if this is what I have in my BlogPost.m class

- (id) initWithTitle:(NSString *)title{
    self = [super init];

    if (self){
        self.title = title;
        self.author = nil;
        self.thumbNail = nil;
    }
    return self;
}
+ (id) blogPostWithTitle:(NSString *)title {
    return [[self alloc] initWithTitle:title];
}

I'm safe to remove the - (id) initWithTitle because they are doing the same thing?

Stone Preston
Stone Preston
42,016 Points
Stone Preston
Stone Preston
42,016 Points

No, you cannot remove initWithTitle because your blogPostWithTitle constructor calls the initWithTitle method as seen below

+ (id) blogPostWithTitle:(NSString *)title {
    return [[self alloc] initWithTitle:title];
}

if you removed it, blogPostWithTitle will not work

gregdodd
gregdodd
8,124 Points
gregdodd
gregdodd
8,124 Points

Don't know how I overlooked that one, thanks! So in this case, what role is the initWithTitle playing? Could I change initWithTitle:title to initWithString: title?

Thanks for the quick responses btw, don't like to move ahead until I've got everything down.