Objects are instance of classes that has its own memory allocated for instance variable/properties. All objects share the memory for the methods. A sample for object instantiation is shown below.

@interface SampleClass:NSObject
// Properties declaration
@property(nonatomic, strong) NSString *string;

// Method declaration
- (void)start:(id)obj;
@end

@implementation SampleClass

- (void)start:(id)obj{
// Method definition
}

@end

int main(int argc, const char * argv[])
{
    //  Autoreleasepool used in main for automatic memory management.
    @autoreleasepool {
        
        // A simple log
        NSLog(@"Hello, World!");
		// Creating object
		SampleClass *sampleClass = [[SampleClass alloc] init];
        // Setting property
		sampleClass.color = @"test";

		// Accessing instance method
	    [sampleClass test];
       
    }
    return 0;
}