多态
多态指的是允许父类的指针指向子类的对象,当指针指向不同的子类对象时,给它发送同一个消息就会有不同的响应.
如下定义一个父类Animal和二个子类Dog,Cat.
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| @interface Animal : NSObject
- (void)run;
+ (void)bark;
+ (void)canClimb:(void(^)(BOOL can))blk;
@end
@implementation Animal
- (void)run
{
NSLog(@"%@ run", self);
}
+ (void)bark {
NSLog(@"%@ bark", self);
}
+ (void)canClimb:(void (^)(BOOL))blk {
!blk ?: blk(NO);
}
@end
...
@implementation Dog
- (void)run
{
NSLog(@"%@ run", self);
}
+ (void)bark {
NSLog(@"%@ bark", self);
}
+ (void)canClimb:(void (^)(BOOL))blk {
!blk ?: blk(NO);
}
@end
...
@implementation Cat
- (void)run
{
NSLog(@"%@ run", self);
}
+ (void)bark {
NSLog(@"%@ bark", self);
}
+ (void)canClimb:(void (^)(BOOL))blk {
!blk ?: blk(YES);
}
@end
|
接下来我们来个反射+多态:
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| NSArray *clsArr = @[@"Animal", @"Dog", @"Cat"];
for (NSString *clsStr in clsArr) {
Class cls = NSClassFromString(clsStr);
id obj = [cls new];
[obj run];
}
for (NSString *clsStr in clsArr) {
Class cls = NSClassFromString(clsStr);
[cls performSelector:@selector(bark)];
}
for (NSString *clsStr in clsArr) {
Class cls = NSClassFromString(clsStr);
[cls canClimb:^(BOOL can){
NSLog(@"%@ can climb:%d",cls, can);
}];
}
for (NSString *clsStr in clsArr) {
Class cls = NSClassFromString(clsStr);
[cls performSelector:@selector(canClimb:) withObject:^(BOOL can){
NSLog(@"%@ can climb:%d",cls, can);
}];
}
|
以上需要注意的是:
Xcode对于id类型调用实例方法,实例方法会有补全提示.对于Class类型调用类方法,类方法就没有补全提示,但你写全后也不会报错.
对于类方法的动态调用可以使用performSelector,也可以手动写全,这里Xcode不会自动补全不知道为什么.
