To declare a class in Objective-C, you use the @interface keyword followed by the name of the class, braces, and a list of instance variables and method declarations. Here is an example of declaring a class in Objective-C:
@interface MyClass : NSObject
@property (nonatomic, strong) NSString *name;
- (void)sayHello;
@end
In this example, we are declaring a class called MyClass that inherits from the NSObject class. We have also declared an instance variable called name and a method called sayHello.
The @property declaration is a shorthand syntax for declaring instance variables with their accompanying getter/setter methods. In this case, we are declaring an instance variable called name that is of type NSString and has a strong memory management attribute.
The sayHello method is a simple method that does not return a value and takes no arguments. Its implementation would be defined in the @implementation block for the class.
Once you have declared a class, you can then create instances of it and call its methods using the dot notation syntax. For example:
MyClass *myObject = [[MyClass alloc] init];
myObject.name = @"John";
[myObject sayHello];