如果在缓存中没查找到方法，之后的流程,CheckMiss和JumpMiss的流程一模一样
CheckMiss-->__objc_msgSend_uncached
.macro CheckMiss
// miss if bucket->sel == 0
.if $0 == GETIMP
cbz p9, LGetImpMiss
.elseif $0 == NORMAL
cbz p9, __objc_msgSend_uncached
.elseif $0 == LOOKUP
cbz p9, __objc_msgLookup_uncached
JumpMiss->__objc_msgSend_uncached-> MethodTableLookup->_lookUpImpOrForward
.macro JumpMiss
.if $0 == GETIMP
b LGetImpMiss
.elseif $0 == NORMAL
b __objc_msgSend_uncached
.elseif $0 == LOOKUP
b __objc_msgLookup_uncached
跳入MethodTableLookup
.endmacro
STATIC_ENTRY __objc_msgSend_uncached
UNWIND __objc_msgSend_uncached, FrameWithNoSaves
// THIS IS NOT A CALLABLE C FUNCTION
// Out-of-band p16 is the class to search
MethodTableLookup
TailCallFunctionPointer x17
END_ENTRY __objc_msgSend_uncached
_lookUpImpOrForward
.macro MethodTableLookup
SAVE_REGS
// lookUpImpOrForward(obj, sel, cls, LOOKUP_INITIALIZE | LOOKUP_RESOLVER)
// receiver and selector already in x0 and x1
mov x2, x16
mov x3, #3
bl _lookUpImpOrForward
// IMP in x0
mov x17, x0
RESTORE_REGS
.endmacro
通过代码跑流程的形式查看最终一个方法找不到会走入的流程
通过Debug workflow -> Always show disassembly -> 按住control + stepinto进入汇编调试
23.gif
定位到lookUpImpOrForward at objc-runtime-new.mm:6099行代码
IMP lookUpImpOrForward(id inst, SEL sel, Class cls, int behavior)
{
const IMP forward_imp = (IMP)_objc_msgForward_impcache;
IMP imp = nil;
Class curClass;
runtimeLock.assertUnlocked();
// Optimistic cache lookup
if (fastpath(behavior & LOOKUP_CACHE)) {
imp = cache_getImp(cls, sel);
if (imp) goto done_nolock;
}
// runtimeLock is held during isRealized and isInitialized checking
// to prevent races against concurrent realization.
// runtimeLock is held during method search to make
// method-lookup + cache-fill atomic with respect to method addition.
// Otherwise, a category could be added but ignored indefinitely because
// the cache was re-filled with the old value after the cache flush on
// behalf of the category.
runtimeLock.lock();
// We don't want people to be able to craft a binary blob that looks like
// a class but really isn't one and do a CFI attack.
//
// To make these harder we want to make sure this is a class that was
// either built into the binary or legitimately registered through
// objc_duplicateClass, objc_initializeClassPair or objc_allocateClassPair.
//
// TODO: this check is quite costly during process startup.
checkIsKnownClass(cls);
if (slowpath(!cls->isRealized())) {
cls = realizeClassMaybeSwiftAndLeaveLocked(cls, runtimeLock);
// runtimeLock may have been dropped but is now locked again
}
if (slowpath((behavior & LOOKUP_INITIALIZE) && !cls->isInitialized())) {
cls = initializeAndLeaveLocked(cls, inst, runtimeLock);
// runtimeLock may have been dropped but is now locked again
// If sel == initialize, class_initialize will send +initialize and
// then the messenger will send +initialize again after this
// procedure finishes. Of course, if this is not being called
// from the messenger then it won't happen. 2778172
}
runtimeLock.assertLocked();
curClass = cls;
// The code used to lookpu the class's cache again right after
// we take the lock but for the vast majority of the cases
// evidence shows this is a miss most of the time, hence a time loss.
//
// The only codepath calling into this without having performed some
// kind of cache lookup is class_getInstanceMethod().
for (unsigned attempts = unreasonableClassCount();;) {
// curClass method list.
Method meth = getMethodNoSuper_nolock(curClass, sel);
if (meth) {
imp = meth->imp;
goto done;
}
if (slowpath((curClass = curClass->superclass) == nil)) {
// No implementation found, and method resolver didn't help.
// Use forwarding.
imp = forward_imp;
break;
}
// Halt if there is a cycle in the superclass chain.
if (slowpath(--attempts == 0)) {
_objc_fatal("Memory corruption in class list.");
}
// Superclass cache.
imp = cache_getImp(curClass, sel); // 有问题???? cache_getImp - lookup - lookUpImpOrForward
if (slowpath(imp == forward_imp)) {
// Found a forward:: entry in a superclass.
// Stop searching, but don't cache yet; call method
// resolver for this class first.
break;
}
if (fastpath(imp)) {
// Found the method in a superclass. Cache it in this class.
goto done;
}
}
// No implementation found. Try method resolver once.
if (slowpath(behavior & LOOKUP_RESOLVER)) {
behavior ^= LOOKUP_RESOLVER;
return resolveMethod_locked(inst, sel, cls, behavior);
}
done:
log_and_fill_cache(cls, imp, sel, inst, curClass);
runtimeLock.unlock();
done_nolock:
if (slowpath((behavior & LOOKUP_NIL) && imp == forward_imp)) {
return nil;
}
return imp;
}
探索对象方法的查找流程
对象调用一个没有实现的方法会报错,方法的查找流程是，先从本类中查找，本类中没有往父类中查找
#pragma clang diagnostic push
// 让编译器忽略错误
#pragma clang diagnostic ignored "-Wundeclared-selector"
LGStudent *student = [[LGStudent alloc] init];
// 对象方法
[student sayHello];
[student sayNB];
// unrecognized selector sent to instance 0x103d32010
[student sayMaster];
输出
2020-11-01 11:25:58.294977+0800 002-方法的查找流程[22988:295515] -[LGStudent sayHello]
2020-11-01 11:25:58.295465+0800 002-方法的查找流程[22988:295515] -[LGPerson sayNB]
2020-11-01 11:25:58.295722+0800 002-方法的查找流程[22988:295515] -[LGStudent sayMaster]: unrecognized selector sent to instance 0x100622470
2020-11-01 11:25:58.296273+0800 002-方法的查找流程[22988:295515] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[LGStudent sayMaster]: unrecognized selector sent to instance 0x100622470'
*** First throw call stack:
(
0 CoreFoundation 0x00007fff31e89b57 __exceptionPreprocess + 250
1 libobjc.A.dylib 0x00007fff6acd05bf objc_exception_throw + 48
2 CoreFoundation 0x00007fff31f08be7 -[NSObject(NSObject) __retain_OA] + 0
3 CoreFoundation 0x00007fff31dee3bb ___forwarding___ + 1427
4 CoreFoundation 0x00007fff31dedd98 _CF_forwarding_prep_0 + 120
6 libdyld.dylib 0x00007fff6be78cc9 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
若在NSObject中添加分类来实现sayMaster方法，则方法能找到
@interface NSObject (LGCate)
- (void)sayMaster;
- (void)sayEasy;
@end
@implementation NSObject (LGCate)
- (void)sayMaster{
NSLog(@"%s",__func__);
}
- (void)sayEasy{
NSLog(@"%s",__func__);
}
@end
//输出
2020-11-01 11:37:31.406340+0800 002-方法的查找流程[30058:313811] -[LGStudent sayHello]
2020-11-01 11:37:31.406764+0800 002-方法的查找流程[30058:313811] -[LGPerson sayNB]
2020-11-01 11:37:31.406844+0800 002-方法的查找流程[30058:313811] -[NSObject(LGCate) sayMaster]
如果是类中的一个类方法没有实现呢？
LGStudent中没有类方法sayEasy,运行会报错*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '+[LGStudent sayEasy]: unrecognized selector sent to class 0x100002290'
如果在NSObject分类中添加对象方法sayEasy，会不会报错？
// 类方法
[LGStudent sayObjc];
[LGStudent sayHappay];
[LGStudent performSelector:@selector(sayEasy)]; // +
@interface NSObject (LGCate)
- (void)sayMaster;
- (void)sayEasy;
@end
@implementation NSObject (LGCate)
- (void)sayMaster{
NSLog(@"%s",__func__);
}
- (void)sayEasy{
NSLog(@"%s",__func__);
}
@end
//输出
2020-11-01 11:49:25.780317+0800 002-方法的查找流程[37381:333382] -[LGStudent sayHello]
2020-11-01 11:49:25.780738+0800 002-方法的查找流程[37381:333382] -[LGPerson sayNB]
2020-11-01 11:49:25.780785+0800 002-方法的查找流程[37381:333382] -[NSObject(LGCate) sayMaster]
2020-11-01 11:49:25.780817+0800 002-方法的查找流程[37381:333382] +[LGStudent sayObjc]
2020-11-01 11:49:25.780846+0800 002-方法的查找流程[37381:333382] +[LGPerson sayHappay]
2020-11-01 11:49:25.780877+0800 002-方法的查找流程[37381:333382] -[NSObject(LGCate) sayEasy]
根据ISA走位图
isa流程图.png
得到对象方法的查找流程
类->父类->NSObject->nil
类方法的查找流程，类方法存在元类里面
类方法在元类中是以对象方法的形式存在的
元类->父元类->根元类->NSObject->nil
NSObject分类中存在sayEasy的对象方法，即能找到，万物皆会找到NSObject里面，Root class meta(NSObject)中没有找到sayEasy的对象方法，则找根元类的父类Root class(NSObject)的实例方法，因为继承关系
方法的慢速查找流程
方法的慢速查找流程.png
通过阅读源码理解方法的慢速查找流程
lookUpImpOrForward
- 1.获取多线程中是否存在缓存的Imp，若存在可理解返回imp = cache_getImp(cls, sel);
- 2.判断类是否已知checkIsKnownClass(cls);
- 3.判断类是否实现和类checkIsKnownClass(cls);
- 4.进行二分查找获取类中方法的总数，进行递归
for (unsigned attempts = unreasonableClassCount();;) {
// curClass method list.
//本类中查找
Method meth = getMethodNoSuper_nolock(curClass, sel);
if (meth) {
imp = meth->imp;
goto done;
}
//当前的类赋值为父类
if (slowpath((curClass = curClass->superclass) == nil)) {
// No implementation found, and method resolver didn't help.
// Use forwarding.
imp = forward_imp;
break;
}
// Halt if there is a cycle in the superclass chain.
if (slowpath(--attempts == 0)) {
_objc_fatal("Memory corruption in class list.");
}
// Superclass cache.
//从父类的缓存中查找
imp = cache_getImp(curClass, sel);
if (slowpath(imp == forward_imp)) {
// Found a forward:: entry in a superclass.
// Stop searching, but don't cache yet; call method
// resolver for this class first.
break;
}
if (fastpath(imp)) {
// Found the method in a superclass. Cache it in this class.
goto done;
}
}
先从本类中查找，二分查找
@interface LGPerson : NSObject
@property (nonatomic, copy) NSString *lgName;
@property (nonatomic, strong) NSString *nickName;
- (void)sayNB;
- (void)sayMaster;
- (void)say666;
- (void)sayHello;
@end
@implementation LGPerson
- (void)sayHello{
NSLog(@"%s",__func__);
}
- (void)sayNB{
NSLog(@"%s",__func__);
}
- (void)sayMaster{
NSLog(@"%s",__func__);
}
- (void)say666{
NSLog(@"%s",__func__);
}
@end
从上面可以得知类中含有8个方法，分别为sayHello,sayNB,sayMaster,say666，setLgName:,setNickName:,lgName,nickName;
ALWAYS_INLINE static method_t *
search_method_list_inline(const method_list_t *mlist, SEL sel)
{
int methodListIsFixedUp = mlist->isFixedUp();
int methodListHasExpectedSize = mlist->entsize() == sizeof(method_t);
if (fastpath(methodListIsFixedUp && methodListHasExpectedSize)) {
return findMethodInSortedMethodList(sel, mlist);
} else {
// Linear search of unsorted method list
for (auto& meth : *mlist) {
if (meth.name == sel) return &meth;
}
}
#if DEBUG
// sanity-check negative results
if (mlist->isFixedUp()) {
for (auto& meth : *mlist) {
if (meth.name == sel) {
_objc_fatal("linear search worked when binary search did not");
}
}
}
#endif
return nil;
}
ALWAYS_INLINE static method_t *
findMethodInSortedMethodList(SEL key, const method_list_t *list)
{
ASSERT(list);
const method_t * const first = &list->first;
const method_t *base = first;
const method_t *probe;
uintptr_t keyValue = (uintptr_t)key;
uint32_t count;
for (count = list->count; count != 0; count >>= 1) {
probe = base + (count >> 1);
uintptr_t probeValue = (uintptr_t)probe->name;
if (keyValue == probeValue) {
// `probe` is a match.
// Rewind looking for the *first* occurrence of this value.
// This is required for correct category overrides.
while (probe > first && keyValue == (uintptr_t)probe[-1].name) {
probe--;
}
return (method_t *)probe;
}
if (keyValue > probeValue) {
base = probe + 1;
count--;
}
}
return nil;
}
通过调试mlist存在9个方法，除了类中的8个方法外多了一个C++方法.cxx_destruct
(lldb) p mlist
(const method_list_t *) $0 = 0x00000001000020c8
(lldb) p *$0
(const method_list_t) $1 = {
entsize_list_tt<method_t, method_list_t, 3> = {
entsizeAndFlags = 26
count = 9
first = {
name = "sayHello"
types = 0x0000000100000f86 "v16@0:8"
imp = 0x0000000100000c40 (KCObjc`-[LGPerson sayHello])
}
}
}
(lldb) p $1.get(0)
(method_t) $2 = {
name = "sayHello"
types = 0x0000000100000f86 "v16@0:8"
imp = 0x0000000100000c40 (KCObjc`-[LGPerson sayHello])
}
(lldb) p $1.get(1)
(method_t) $3 = {
name = "say666"
types = 0x0000000100000f86 "v16@0:8"
imp = 0x0000000100000cd0 (KCObjc`-[LGPerson say666])
}
(lldb) p $1.get(2)
(method_t) $4 = {
name = "sayNB"
types = 0x0000000100000f86 "v16@0:8"
imp = 0x0000000100000c70 (KCObjc`-[LGPerson sayNB])
}
(lldb) p $1.get(3)
(method_t) $5 = {
name = "sayMaster"
types = 0x0000000100000f86 "v16@0:8"
imp = 0x0000000100000ca0 (KCObjc`-[LGPerson sayMaster])
}
(lldb) p $1.get(4)
(method_t) $6 = {
name = "lgName"
types = 0x0000000100000f8e "@16@0:8"
imp = 0x0000000100000d00 (KCObjc`-[LGPerson lgName])
}
(lldb) p $1.get(5)
(method_t) $7 = {
name = "setLgName:"
types = 0x0000000100000f96 "v24@0:8@16"
imp = 0x0000000100000d30 (KCObjc`-[LGPerson setLgName:])
}
(lldb) p $1.get(6)
(method_t) $8 = {
name = ".cxx_destruct"
types = 0x0000000100000f86 "v16@0:8"
imp = 0x0000000100000db0 (KCObjc`-[LGPerson .cxx_destruct])
}
(lldb) p $1.get(7)
(method_t) $9 = {
name = "setNickName:"
types = 0x0000000100000f96 "v24@0:8@16"
imp = 0x0000000100000d80 (KCObjc`-[LGPerson setNickName:])
}
(lldb) p $1.get(8)
(method_t) $10 = {
name = "nickName"
types = 0x0000000100000f8e "@16@0:8"
imp = 0x0000000100000d60 (KCObjc`-[LGPerson nickName])
}
(lldb) p $1.get(9)
Assertion failed: (i < count), function get, file /Users/cloud/Documents/iOS/0921/20200921--大师班第8节课--消息流程/20200921-大师班第8天-方法查找流程/01--课堂代码/001-objc_msgSend分析探索/runtime/objc-runtime-new.h, line 438.
error: Execution was interrupted, reason: signal SIGABRT.
The process has been returned to the state before expression evaluation.
执行完int methodListIsFixedUp = mlist->isFixedUp()查看mlist中的方法是否排序,还是和之前一样。
(lldb) p mlist
(const method_list_t *) $11 = 0x00000001000020c8
(lldb) p *$0
(const method_list_t) $12 = {
entsize_list_tt<method_t, method_list_t, 3> = {
entsizeAndFlags = 26
count = 9
first = {
name = "sayHello"
types = 0x0000000100000f86 "v16@0:8"
imp = 0x0000000100000c40 (KCObjc`-[LGPerson sayHello])
}
}
}
(lldb) p $12.get(0)
(method_t) $13 = {
name = "sayHello"
types = 0x0000000100000f86 "v16@0:8"
imp = 0x0000000100000c40 (KCObjc`-[LGPerson sayHello])
}
(lldb) p $12.get(1)
(method_t) $14 = {
name = "say666"
types = 0x0000000100000f86 "v16@0:8"
imp = 0x0000000100000cd0 (KCObjc`-[LGPerson say666])
}
(lldb) p $12.get(2)
(method_t) $15 = {
name = "sayNB"
types = 0x0000000100000f86 "v16@0:8"
imp = 0x0000000100000c70 (KCObjc`-[LGPerson sayNB])
}
(lldb) p $12.get(3)
(method_t) $16 = {
name = "sayMaster"
types = 0x0000000100000f86 "v16@0:8"
imp = 0x0000000100000ca0 (KCObjc`-[LGPerson sayMaster])
}
(lldb) p $12.get(4)
(method_t) $17 = {
name = "lgName"
types = 0x0000000100000f8e "@16@0:8"
imp = 0x0000000100000d00 (KCObjc`-[LGPerson lgName])
}
(lldb) p $12.get(5)
(method_t) $18 = {
name = "setLgName:"
types = 0x0000000100000f96 "v24@0:8@16"
imp = 0x0000000100000d30 (KCObjc`-[LGPerson setLgName:])
}
(lldb) p $12.get(6)
(method_t) $19 = {
name = ".cxx_destruct"
types = 0x0000000100000f86 "v16@0:8"
imp = 0x0000000100000db0 (KCObjc`-[LGPerson .cxx_destruct])
}
(lldb) p $12.get(7)
(method_t) $20 = {
name = "setNickName:"
types = 0x0000000100000f96 "v24@0:8@16"
imp = 0x0000000100000d80 (KCObjc`-[LGPerson setNickName:])
}
(lldb) p $12.get(8)
(method_t) $21 = {
name = "nickName"
types = 0x0000000100000f8e "@16@0:8"
imp = 0x0000000100000d60 (KCObjc`-[LGPerson nickName])
}
(lldb) p $12.get(9)
Assertion failed: (i < count), function get, file /Users/cloud/Documents/iOS/0921/20200921--大师班第8节课--消息流程/20200921-大师班第8天-方法查找流程/01--课堂代码/001-objc_msgSend分析探索/runtime/objc-runtime-new.h, line 438.
error: Execution was interrupted, reason: signal SIGABRT.
The process has been returned to the state before expression evaluation.
方法的二分查找流程.png
本类中没有，从父类的缓存中查找
从父类中查找递归
找到返回Imp并将Imp填充缓存
log_and_fill_cache(cls, imp, sel, inst, curClass);方便下次快速查找，没找到则跳入动态方法决议,系统给一个挽救的机会，实现[cls resolveInstanceMethod:sel]方法，
if (slowpath(behavior & LOOKUP_RESOLVER)) {
behavior ^= LOOKUP_RESOLVER;
return resolveMethod_locked(inst, sel, cls, behavior);
}
若都没找到，
return imp == forward_imp
void *_objc_forward_handler = nil;
void *_objc_forward_stret_handler = nil;
#else
// Default forward handler halts the process.
__attribute__((noreturn, cold)) void
objc_defaultForwardHandler(id self, SEL sel)
{
_objc_fatal("%c[%s %s]: unrecognized selector sent to instance %p "
"(no message forward handler is installed)",
class_isMetaClass(object_getClass(self)) ? '+' : '-',
object_getClassName(self), sel_getName(sel), self);
}
void *_objc_forward_handler = (void*)objc_defaultForwardHandler;
将say666对象方法注释掉，报错如下
//- (void)say666{
// NSLog(@"%s",__func__);
//}
2020-11-02 02:48:07.732479+0800 KCObjc[26239:1214027] -[LGPerson sayHello]
2020-11-02 02:48:07.733236+0800 KCObjc[26239:1214027] -[LGPerson say666]: unrecognized selector sent to instance 0x100725e30
2020-11-02 02:48:07.735713+0800 KCObjc[26239:1214027] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[LGPerson say666]: unrecognized selector sent to instance 0x100725e30'
*** First throw call stack:
(
0 CoreFoundation 0x00007fff31e89b57 __exceptionPreprocess + 250
1 libobjc.A.dylib 0x00000001002d15ba objc_exception_throw + 42
2 CoreFoundation 0x00007fff31f08be7 -[NSObject(NSObject) __retain_OA] + 0
3 CoreFoundation 0x00007fff31dee3bb ___forwarding___ + 1427
4 CoreFoundation 0x00007fff31dedd98 _CF_forwarding_prep_0 + 120
5 KCObjc 0x0000000100000c61 main + 81
6 libdyld.dylib 0x00007fff6be78cc9 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
不存在所谓的“+”和“-”方法，底层都为函数
动态方法决议
一直没有找到方法的Imp,在报错之前，系统给一次挽救的机会，在LGPerson中是否实现了类方法+ (BOOL)resolveInstanceMethod:(SEL)sel，SEL resolve_sel = @selector(resolveInstanceMethod:);,在LGPerson的元类中找实例方法!lookUpImpOrNil(cls, resolve_sel, cls->ISA()),如果存在，则重新进行慢速查找一遍，看类中是否存在say666方法，存在即返回，不存在就执行报错的forward_imp
// No implementation found. Try method resolver once.
if (slowpath(behavior & LOOKUP_RESOLVER)) {
behavior ^= LOOKUP_RESOLVER;
return resolveMethod_locked(inst, sel, cls, behavior);
}
static NEVER_INLINE IMP
resolveMethod_locked(id inst, SEL sel, Class cls, int behavior)
{
runtimeLock.assertLocked();
ASSERT(cls->isRealized());
runtimeLock.unlock();
if (! cls->isMetaClass()) {
// try [cls resolveInstanceMethod:sel]
resolveInstanceMethod(inst, sel, cls);
}
else {
// try [nonMetaClass resolveClassMethod:sel]
// and [cls resolveInstanceMethod:sel]
resolveClassMethod(inst, sel, cls);
if (!lookUpImpOrNil(inst, sel, cls)) {
resolveInstanceMethod(inst, sel, cls);
}
}
// chances are that calling the resolver have populated the cache
// so attempt using it
return lookUpImpOrForward(inst, sel, cls, behavior | LOOKUP_CACHE);
}
static void resolveInstanceMethod(id inst, SEL sel, Class cls)
{
runtimeLock.assertUnlocked();
ASSERT(cls->isRealized());
SEL resolve_sel = @selector(resolveInstanceMethod:);
if (!lookUpImpOrNil(cls, resolve_sel, cls->ISA())) {
// Resolver not implemented.
return;
}
BOOL (*msg)(Class, SEL, SEL) = (typeof(msg))objc_msgSend;
bool resolved = msg(cls, resolve_sel, sel);
// Cache the result (good or bad) so the resolver doesn't fire next time.
// +resolveInstanceMethod adds to self a.k.a. cls
IMP imp = lookUpImpOrNil(inst, sel, cls);
if (resolved && PrintResolving) {
if (imp) {
_objc_inform("RESOLVE: method %c[%s %s] "
"dynamically resolved to %p",
cls->isMetaClass() ? '+' : '-',
cls->nameForLogging(), sel_getName(sel), imp);
}
else {
// Method resolver didn't add anything?
_objc_inform("RESOLVE: +[%s resolveInstanceMethod:%s] returned YES"
", but no new implementation of %c[%s %s] was found",
cls->nameForLogging(), sel_getName(sel),
cls->isMetaClass() ? '+' : '-',
cls->nameForLogging(), sel_getName(sel));
}
}
}
+ (BOOL)resolveInstanceMethod:(SEL)sel{
if (sel == @selector(say666)) {
NSLog(@"%@ 来了哦",NSStringFromSelector(sel));
IMP imp = class_getMethodImplementation(self, @selector(sayMaster));
Method sayMMethod = class_getInstanceMethod(self, @selector(sayMaster));
const char *type = method_getTypeEncoding(sayMMethod);
return class_addMethod(self, sel, imp, type);
}
return [super resolveInstanceMethod:sel];
}
//输出
2020-11-03 01:10:58.078990+0800 KCObjc[527:426803] -[LGPerson sayHello]
2020-11-03 01:10:58.079698+0800 KCObjc[527:426803] say666 来了哦
2020-11-03 01:10:58.079928+0800 KCObjc[527:426803] -[LGPerson sayMaster]
动态方法决议@2x.png
LGPerson分类中存在同名的sayHell0方法，则二分查找流程如下
方法的二分查找分类中有同名的方法.png
分类同名方法.png
main@2x.png
