In Objective-C, classes and objects serve as the backbone for software structure. A class typically consists of interface and implementation sections.

Interface

The class interface lists the properties and methods that are accessible to other classes, essentially acting as a public API.

Here is the Objective-C code:

@interface MyClass : NSObject

@property NSString *name;

- (void)someMethod;

@end

It begins with @interface, the class identifier (MyClass), and a base class (usually NSObject). The list following @interface comprises Instance Variables (if any), Properties, and Method Declarations (optional) visible to other classes.

Properties

Properties define attributes accessed via getter and setter methods, offering a more controlled means of manipulating an object’s state. Attributes like atomicity, memory management, and runtime behavior can be specified.

Here is the Objective-C code:

@interface MyClass : NSObject

@property (atomic, strong) NSString *name;

- (void)someMethod;

@end

The simplified form of a property in Objective-C would look like this:

@property NSString *name;

Note: Custom getter and setter methods can be defined for additional control.

Methods

Method declarations specify the class’s behavior. They may be singleton methods (denoted by a + symbol) or instance methods (denoted by a - symbol).

Here is the Objective-C code:

@interface MyClass : NSObject

- (void)methodOne;
- (NSInteger)methodReturningIntegerWithParameter:(NSString *)param;

+ (void)classMethodOne;

@end

Instance Variables

In modern Objective-C, it’s a best practice to directly access the instance variables via property accessors, as shown below:

@implementation MyClass
{
    NSString *_internalName;
}

- (void)setInternalName(NSString *)name {
    _internalName = name;
}
- (NSString *)internalName {
    return _internalName;
}
@end

However, in older Objective-C code, the explicit declaration was used as shown here:

@interface MyClass : NSObject
{
    NSString *_internalName;
}
@end

Implementation

The @implementation section describes how class methods and instance methods are defined.

Here is the Objective-C code:

@implementation MyClass

- (void)someMethod {
    // Implementation here
}

+ (void)classMethodOne {
    // Class method implementation here
}

@end

The @implementation section is typically followed by method definitions, along with any additional internal methods that are not part of the interface.