Runtime的简单使用

有一个Person类

@interface Person : NSObject@property (nonatomic, copy) NSString * name;@property (nonatomic, copy) NSString * adress;- (NSString *)first;- (NSString *)second;@end

@implementation Person- (NSString *)first {    NSLog(@"11111111");    return @"first";}- (NSString *)second {    NSLog(@"222222222");    return @"second";}@end

self.person = [[Person alloc] init];self.person.adress = @"shanghai";self.person.name = @"xiaoming";

1.动态修改实例变量的值

unsigned int count = 0;    Ivar * ivar = class_copyIvarList([self.person class], &count);    for (int i = 0; i < count; i++) {        Ivar var = ivar[i];        const char * varName = ivar_getName(var);        NSString * name = [NSString stringWithUTF8String:varName];        if ([name isEqualToString:@"_name"]) {            object_setIvar(self.person, var, @"是是是");            break;        }    }    self.nameLab.text = self.person.name;

2.动态交换2个方法的实现

Method m1 = class_getInstanceMethod([self.person class], @selector(first));    Method m2 = class_getInstanceMethod([self.person class], @selector(second));    method_exchangeImplementations(m1, m2);   //m1的实现被替换为m2的实现    NSString * firstReturn = [self.person first];    self.nameLab.text = firstReturn;

3.动态添加方法

class_addMethod([self.person class], @selector(guessAns), (IMP)guessAns, "v@:");    if ([self.person respondsToSelector:@selector(guessAns)]) {        [self.person performSelector:@selector(guessAns)];    } else {        NSLog(@"gasfs");    }    self.nameLab.text = @"5555";

添加的方法

void guessAns(id self, SEL _cmd) {    NSLog(@"hello world");}