It’s possible to add formal properties to a class via class_addProperty(): BOOL class_addProperty(Class cls, const char *name, const objc_property_attribute_t *attributes, unsigned int attributeCount) The first two parameters are self-explanatory. The third parameter is an array of property attributes, and each property attribute is a name-value pair which follow Objective-C type encodings for declared properties. Note … Read more
Both answers were correct but I want to clarify a little bit more. _ is used to modify external parameter name behavior for methods. In Local and External Parameter Names for Methods section of the documentation, it says: Swift gives the first parameter name in a method a local parameter name by default, and gives … Read more
I know this was extremely frustrating for me as a beginning programmer, or even as a moderately skilled one now. File I/O through the Mail and Safari apps involves very… interestingly named conventions within the app itself. So let’s get our hands dirty with an Xcode project for iPhone. Open Xcode (I will be using … Read more
How are Obj-C messages dispatched? Objective-C messages are dispatched using the runtime’s objc_msgSend() function. Shown in the Apple docs, the function takes at least 2 arguments: The receiving object The selector of the message [A variable list of arguments to the message being sent.] Instances of a class have an isa pointer, which is a … Read more
In Objective-C, a selector’s signature consists of: The name of the method (in this case it would be ‘myTest’) (required) A ‘:’ (colon) following the method name if the method has an input. A name and ‘:’ for every additional input. Selectors have no knowledge of: The input types The method’s return type. Here’s a … Read more
The basic concept is to use the UIBezierPath class to your advantage. You are able to draw arcs, which achieve the effect you’re after. I’ve only had half an hour or so to have a crack at this, but my attempt is below. Very rudimentary, it simply uses a stroke on the path, but here … Read more
1) Define your own completion block, typedef void(^myCompletion)(BOOL); 2) Create a method which takes your completion block as a parameter, -(void) myMethod:(myCompletion) compblock{ //do stuff compblock(YES); } 3)This is how you use it, [self myMethod:^(BOOL finished) { if(finished){ NSLog(@”success”); } }];
They differ in their types. They’re all zero, but NULL is a void *, nil is an id, and Nil is a Class pointer.
As always with reference types, there are two notions of “copy”. I’m sure you know them, but for completeness. A bitwise copy. In this, we just copy the memory bit for bit – this is what NSCopyObject does. Nearly always, it’s not what you want. Objects have internal state, other objects, etc, and often make … Read more
Use Instruments to track down deallocated instance errors. Profile your application (Cmd ⌘+I) and choose Zombies template. After your application is running, try to crash it. You should get something like that: Click on the arrow next to address in the popover to show object that was called after it was deallocated. You should see … Read more