class_getInstanceMethod和class_getClassMethod

class_getInstanceMethod     得到类的实例方法

class_getClassMethod          得到类的类方法

/**  * Returns a specified instance method for a given class. *  * @param cls The class you want to inspect. * @param name The selector of the method you want to retrieve. *  * @return The method that corresponds to the implementation of the selector specified by  *  \e name for the class specified by \e cls, or \c NULL if the specified class or its  *  superclasses do not contain an instance method with the specified selector. * * @note This function searches superclasses for implementations, whereas \c class_copyMethodList does not. */OBJC_EXPORT Method class_getInstanceMethod(Class cls, SEL name)    __OSX_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);/**  * Returns a pointer to the data structure describing a given class method for a given class. *  * @param cls A pointer to a class definition. Pass the class that contains the method you want to retrieve. * @param name A pointer of type \c SEL. Pass the selector of the method you want to retrieve. *  * @return A pointer to the \c Method data structure that corresponds to the implementation of the  *  selector specified by aSelector for the class specified by aClass, or NULL if the specified  *  class or its superclasses do not contain an instance method with the specified selector. * * @note Note that this function searches superclasses for implementations,  *  whereas \c class_copyMethodList does not. */OBJC_EXPORT Method class_getClassMethod(Class cls, SEL name)    __OSX_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);

测试所用Person类：

#import <Foundation/Foundation.h>@interface Person : NSObject@property(nonatomic, assign) NSInteger age;@property(nonatomic, copy) NSString * name;+(Person *)sharedManager;- (instancetype)init;+ (void) printDZ;- (void) printDZL;@end#import "Person.h"@interface Person ()@property(nonatomic, strong) NSString * sex;@end@implementation Person+(Person *)sharedManager{    static Person *sharedManager;    static dispatch_once_t onceTest;    dispatch_once(&onceTest, ^{        sharedManager = [[Person alloc] init];    });    NSLog(@"+ method");    return sharedManager;}- (instancetype)init{    self = [super init];    if (self) {        self = [super init];        self.sex = @"-----------";        self.age = 19;        self.name = @"sb";    }    return self;}+ (void)printDZ{    NSLog(@"this is a class method");}- (void)printDZL{    NSLog(@"this is a instance method");}@end

测试代码：

- (void)viewDidLoad {    [super viewDidLoad];    // Do any additional setup after loading the view, typically from a nib.        Person * p1 = [[Person alloc] init];        Method m1 = class_getInstanceMethod([p1 class], @selector(printDZL));    Method m2 = class_getClassMethod([Person class], @selector(printDZ));    NSLog(@"测试前：");    [p1 printDZL];    [Person printDZ];    method_exchangeImplementations(m1, m2);    NSLog(@"测试后：");    [p1 printDZL];    [Person printDZ];     }

输出：

2015-11-04 13:37:08.539 02-runtime[2776:69899] 测试前：2015-11-04 13:37:08.539 02-runtime[2776:69899] this is a instance method2015-11-04 13:37:08.539 02-runtime[2776:69899] this is a class method2015-11-04 13:37:08.540 02-runtime[2776:69899] 测试后：2015-11-04 13:37:08.540 02-runtime[2776:69899] this is a class method2015-11-04 13:37:08.540 02-runtime[2776:69899] this is a instance method

由输出可见，方法体交换了，说明class_getInstanceMethod成功得到了实例方法，class_getClassMethod成功得到了类方法

但是当用class_getInstanceMethod来取类方法，用class_getClassMethod来取实例方法时：

- (void)viewDidLoad {    [super viewDidLoad];    // Do any additional setup after loading the view, typically from a nib.        Person * p1 = [[Person alloc] init];    //    Method m1 = class_getInstanceMethod([p1 class], @selector(printDZL));//    Method m2 = class_getClassMethod([Person class], @selector(printDZ));    Method m1 = class_getInstanceMethod([Person class], @selector(printDZ));    Method m2 = class_getClassMethod([p1 class], @selector(printDZL));    NSLog(@"测试前：");    [p1 printDZL];    [Person printDZ];    method_exchangeImplementations(m1, m2);    NSLog(@"测试后：");    [p1 printDZL];    [Person printDZ];}

输出：

2015-11-04 13:38:10.050 02-runtime[2793:70426] 测试前：2015-11-04 13:38:10.051 02-runtime[2793:70426] this is a instance method2015-11-04 13:38:10.051 02-runtime[2793:70426] this is a class method2015-11-04 13:38:10.051 02-runtime[2793:70426] 测试后：2015-11-04 13:38:10.051 02-runtime[2793:70426] this is a instance method2015-11-04 13:38:10.051 02-runtime[2793:70426] this is a class method

由输出可见，没有发生交换，可知这样是取不到的。