runtime簡稱運行時

        我們都知道Object-C是一種是根據C語言所衍生出來的語言，因此我們的代碼在程序運行過程中都會被轉化成C代碼執行，而runtime就相當于這個橋梁,對于一個想要真正理解OC語言的人，學習runtime是必不可少的，好比想要深刻理解java，映射是必不可少一樣。

例如[objc logMyInfo];會被轉化成objc_msgSend(objc, @selector(logMyInfo));。

OC中一切都被設計成了對象，我們都知道一個類被初始化成一個實例，這個實例是一個對象。實際上一個類本質上也是一個對象，在runtime中用結構體表示。

例如導入#import <objc/runtime.h>我們可以從runtime中看到

/// An opaque type that rePResents a method in a class definition.描述類中的一個方法typedef struct objc_method *Method;/// An opaque type that represents an instance variable.實例變量typedef struct objc_ivar *Ivar;/// An opaque type that represents a category. 類別Categorytypedef struct objc_category *Category;/// An opaque type that represents an Objective-C declared property.類中聲明的屬性typedef struct objc_property *objc_property_t;//類在runtime中的表示struct objc_class {    Class isa  OBJC_ISA_AVAILABILITY;    //指針，顧名思義，表示是一個什么，    //實例的isa指向類對象，類對象的isa指向元類#if !__OBJC2__    //父類    Class super_class                                        OBJC2_UNAVAILABLE;    //類名    const char *name                                         OBJC2_UNAVAILABLE;    long version                                             OBJC2_UNAVAILABLE;    long info                                                OBJC2_UNAVAILABLE;    long instance_size                                       OBJC2_UNAVAILABLE;    //成員變量列表    struct objc_ivar_list *ivars                             OBJC2_UNAVAILABLE;    //方法列表    struct objc_method_list **methodLists                    OBJC2_UNAVAILABLE;    //緩存  一種優化，調用過的方法存入緩存列表，下次調用先找緩存    struct objc_cache *cache                                 OBJC2_UNAVAILABLE;    //協議列表    struct objc_protocol_list *protocols                     OBJC2_UNAVAILABLE;#endif    } OBJC2_UNAVAILABLE;
實戰應用，獲取類屬性列表
1、首先我們先新建一個工程，然后創建一個測試類文件TestClass.h
2、然后新建一些測試類屬性，代碼如下
h文件
#import <Foundation/Foundation.h>@protocol TestDelegate <NSObject>- (void)testDelegateMethod;@end@interface TestClass : NSObject@property (nonatomic,weak) id<TestDelegate> delegate;@property (nonatomic,strong) NSString *outPrOne;- (void)thisTestMethod;@end/** 測試代理 */@protocol TestDelegateTwo <NSObject>- (void)testDelegateMethodTwo;@end@interface TestClassTwo : NSObject@property (nonatomic,weak) id<TestDelegateTwo> delegateTwo;- (void)thisTestMethodTwo;@endm文件
#import "TestClass.h"@interface TestClass ()<TestDelegateTwo>@end@implementation TestClass{    NSString *instanceOne;    TestClassTwo *testTwo;}- (instancetype)init{    self = [super init];    if (self) {        testTwo.delegateTwo = self;    }    return self;}- (void)thisTestMethod{    if ([self.delegate respondsToSelector:@selector(testDelegateMethod)]) {        [self.delegate testDelegateMethod];    }    [testTwo thisTestMethodTwo];}- (void)testDelegateMethodTwo{    NSLog(@"thisTestMethodTwo");}@end@implementation TestClassTwo- (void)thisTestMethodTwo{    if ([self.delegateTwo respondsToSelector:@selector(testDelegateMethodTwo)]) {        [self.delegateTwo testDelegateMethodTwo];    }}@end 3、然后在viewController新建此類，進行測試，代碼如下
#import "ViewController.h"#import "TestClass.h"#import <objc/runtime.h>@interface ViewController ()<TestDelegate>@property (nonatomic,strong) TestClass *testClass;@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    _testClass = [TestClass new];    _testClass.delegate = self;    unsigned int count;    //獲取屬性列表    objc_property_t *propertyList = class_copyPropertyList([_testClass class], &count);    for (int i=0; i<count; i++) {        const char *propertyName = property_getName(propertyList[i]);        NSLog(@"property---->%@", [NSString stringWithUTF8String:propertyName]);    }        //獲取方法列表    Method *methodList = class_copyMethodList([_testClass class], &count);    for (int i=0; i<count; i++) {        Method method = methodList[i];        NSLog(@"method---->%@", NSStringFromSelector(method_getName(method)));    }        //獲取成員變量列表    Ivar *ivarList = class_copyIvarList([_testClass class], &count);    for (int i=0; i<count; i++) {        Ivar myIvar = ivarList[i];        const char *ivarName = ivar_getName(myIvar);        NSLog(@"Ivar---->%@", [NSString stringWithUTF8String:ivarName]);    }    [_testClass thisTestMethod];    //獲取協議列表    __unsafe_unretained Protocol **protocolList = class_copyProtocolList([_testClass class], &count);    for (int i=0; i<count; i++) {        Protocol *myProtocal = protocolList[i];        const char *protocolName = protocol_getName(myProtocal);        NSLog(@"protocol---->%@", [NSString stringWithUTF8String:protocolName]);    }}- (void)testDelegateMethod{    NSLog(@"12111");}控制臺輸出如下
2017-02-06 18:34:39.920 RuntimeDemo[10997:466991] property---->innerPrOne2017-02-06 18:34:39.921 RuntimeDemo[10997:466991] property---->delegate2017-02-06 18:34:39.921 RuntimeDemo[10997:466991] property---->outPrOne2017-02-06 18:34:39.922 RuntimeDemo[10997:466991] property---->hash2017-02-06 18:34:39.922 RuntimeDemo[10997:466991] property---->superclass2017-02-06 18:34:39.923 RuntimeDemo[10997:466991] property---->description2017-02-06 18:34:39.923 RuntimeDemo[10997:466991] property---->debugDescription2017-02-06 18:34:39.924 RuntimeDemo[10997:466991] method---->testDelegateMethodTwo2017-02-06 18:34:39.925 RuntimeDemo[10997:466991] method---->thisTestMethod2017-02-06 18:34:39.926 RuntimeDemo[10997:466991] method---->outPrOne2017-02-06 18:34:39.926 RuntimeDemo[10997:466991] method---->setOutPrOne:2017-02-06 18:34:39.927 RuntimeDemo[10997:466991] method---->innerPrOne2017-02-06 18:34:39.927 RuntimeDemo[10997:466991] method---->setInnerPrOne:2017-02-06 18:34:39.928 RuntimeDemo[10997:466991] method---->.cxx_destruct2017-02-06 18:34:39.928 RuntimeDemo[10997:466991] method---->setDelegate:2017-02-06 18:34:39.929 RuntimeDemo[10997:466991] method---->delegate2017-02-06 18:34:39.929 RuntimeDemo[10997:466991] method---->init2017-02-06 18:34:39.930 RuntimeDemo[10997:466991] Ivar---->instanceOne2017-02-06 18:34:39.931 RuntimeDemo[10997:466991] Ivar---->testTwo2017-02-06 18:34:39.931 RuntimeDemo[10997:466991] Ivar---->_delegate2017-02-06 18:34:39.932 RuntimeDemo[10997:466991] Ivar---->_outPrOne2017-02-06 18:34:39.932 RuntimeDemo[10997:466991] Ivar---->_innerPrOne2017-02-06 18:34:39.933 RuntimeDemo[10997:466991] 121112017-02-06 18:34:39.933 RuntimeDemo[10997:466991] protocol---->TestDelegateTwo由此可知此類所有屬性與方法，以及該類所遵守的協議在下一篇文章我們將介紹如何運用Runtime進行方法攔截