Objective-C 编译器指令简介
@class
声明某个类但不需要引入头文件
@class TempClass
获取某个类
NSString *ClassName = @"TempClass";
Class c = @class(TempClass); ❌
Class c = [TempClass class]; ❓
Class c = NSClassFromString(ClassName); ✔️
@end
类,协议或者接口结束标示
@protocol @required @optional
协议的开始
@protocol TempProtocol <aProtocol,anotherProtocol>
获取某个协议
Protocol *aProtocol = @protocol(TempProtocol);
协议中方法分为必选和可选
@required
-(void)method1;
@optional
-(void)method2;
判断使用协议的类是否响应方法
[object respondsToSelector:@selector(method2)];
@interface @public @package @protected @private @property
标示类或者分类的开始,objc的类基本都是直接间接的继承自NSObject类,我们使用@interface来声明某个类符合某个协议
@interface TempClass:SuperClass<aProtocol,anotherProtocol>{
@public
//instance variables
@package
//instance variables
@protected
//instance variables
@private
//instance variables
}
//property declarations
@property (atomic, readwrite, assign) id aProperty;
//public instance and/or class method declarations
@end
Category
分类(非正式协议)
@interface TempClass(CategoryName)<aProtocol,anotherProtocol>
在.m文件中如果声明的方法是私有的,可以省略CategoryName。(扩展)
assign(default),retain,copy
atomic(default),nonatomic
weak(default),strong
@selector
返回SEL类型的objc方法，如果方法没有声明或者不存在，那么编译器会发出警告。
-(void)aMethod{
SEL aMethodSelector = @selector(aMethod);
[self performSelector:aMethodSelector];
}
@implementation
标示某个类或者分类实现的开始
@synthesize
自动生成属性的实例变量和setter/getter方法
@synthesize aProperty = _aProperty;
@dynamic
用以修饰的属性会在程序运行时动态绑定setter和getter方法
static NSString * const stockCodeHandler = @"stockCodeHandler";
static NSString * const stockMarketHandler = @"stockMarketHandler";
@implementation UIButton (stockButton)
@dynamic stockCode;
@dynamic stockMarket;
-(void)setStockCode:(NSString *)stockCode{
objc_setAssociatedObject(self, (__bridge const void *)(stockCodeHandler), stockCode, OBJC_ASSOCIATION_COPY_NONATOMIC);
}
-(void)setStockMarket:(NSString *)stockMarket{
objc_setAssociatedObject(self, (__bridge const void *)(stockMarketHandler), stockMarket, OBJC_ASSOCIATION_COPY_NONATOMIC);
}
-(NSString *)stockCode{
return objc_getAssociatedObject(self, (__bridge const void *)(stockCodeHandler));
}
-(NSString *)stockMarket{
return objc_getAssociatedObject(self, (__bridge const void *)(stockMarketHandler));
}
-(void)dealloc{
objc_removeAssociatedObjects(self);
}
@end
-(void)btnClick:(UIButton *)sender{
NSLog(@"%@,%@",sender.stockCode,sender.stockMarket);
}
@synchronized
线程锁
-(void)aMethodWithObject:(id)object{
@synchronized(object){
//code that works with locked object
}
}
@throw @try @catch @finally
捕获异常,objc用的少,c#,java使用的多。objc一般使用NSError来处理错误。出于效率考虑。
@try {
NSException *exception = [NSException exceptionWithName:@"ExampleException" reason:@"In your face!" userInfo:nil];
@throw exception;
}
@catch (NSException *exception) {
//Handle an exception thrown in the @try block
}
@finally {
//Code that gets executed whether or not an exception is thrown
}
@autoreleasepool
自动释放池,比原来NSAutoreleasePool快六倍(真的假的…)
@autoreleasepool{
//code
}
@encode
返回类型的符号
char *x = @encode(int);
char *y = @encode(@selector(aMethod)); //y = ":"
if(x = "i"){
}
@compatibility_alias
用于给某个类起别名,这样你就可以使用别名来调用这个类
@compatibility_alias AliasClassName ExistingClassName