Objective C 定义 UIColor 常量

Objective C 是一种面向对象的编程语言，它是苹果公司为开发 iOS 和 macOS 应用程序而创建的。在 Objective C 中，我们可以使用 UIColor 类来表示和操作颜色。UIColor 提供了一些常量，可以直接使用这些常量来表示不同的颜色。

objective-c
UIColor *black = [UIColor blackColor];
UIColor *white = [UIColor whiteColor];
UIColor *red = [UIColor redColor];

objective-c
UIColor *customBlue = [UIColor colorWithRed:0.0f green:0.0f blue:1.0f alpha:1.0f];

objective-c
#import 
@interface ViewController : UIViewController
@end
@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    
    // 创建黑色块
    UIView *blackView = [[UIView alloc] initWithFrame:CGRectMake(50, 50, 100, 100)];
    blackView.backgroundColor = [UIColor blackColor];
    [self.view addSubview:blackView];
    
    // 创建红色块
    UIView *redView = [[UIView alloc] initWithFrame:CGRectMake(200, 50, 100, 100)];
    redView.backgroundColor = [UIColor redColor];
    [self.view addSubview:redView];
    
    // 创建自定义蓝色块
    UIView *customBlueView = [[UIView alloc] initWithFrame:CGRectMake(50, 200, 100, 100)];
    customBlueView.backgroundColor = [UIColor colorWithRed:0.0f green:0.0f blue:1.0f alpha:1.0f];
    [self.view addSubview:customBlueView];
}
@end