iOS底层-类的加载（中）-六虎

上一篇咱们根究到了readClass函数，仅仅对函数姓名进行了赋值，并没有对ro和rw进行操作，本篇咱们就持续根究_read_images函数剩余的调用。

realizeClass的引入

由于咱们根究的目的是类的加载，变量的界说咱们先疏忽protocol和cat实例化数组egorieappointments的当地。为了调试代码，咱们首先仍是先创立一个JSPerson类：

@interface JSPerson : NSObject
@property (nonatomic, strong) NSString *nickName;

- (vo实例化一个类id)say1;
- (void)say2;

+ (void)sayHappy;
@end

#import "JSPerson.h"
@源码编辑器implementation JSPe实例化类rson

- (void)实例化目标是什么意思say1{
 NSLog(@"JSPerson say : %s",变量是什么意思__func__);
}
- (void)say2{
 NSLog(@"JSPerson say : %s",__func__);
}

+ (void)load{
 NSLog(@"load");
}
+ (void)sayHappy{
 NSLog(@"JSPerson say : %s"实例化目标是什么意思,__func__);
}
@end

接下来咱们持续看_read_images函数，发现和类相关的当地有两个当地，realize non-lazy classes和realize futureSwift classes，咱们在swift代码是什么意思两段代码中参加咱们调试的代码，为了调查咱们自界说类的加载情况:

  // R实例化servlet类异常ealize non-lazy classes (for +load methods and static instances)
 for (EACH_HEADER) {
   cswiftcode代码查询lassref_t const *classlist = hi->nlclslist(&count);
   for (i = 0; i < count; i++) {
     Class cls = remapClass(classlist[i]);
     if (!clapproachs) continue;
     ///调试代码 确定是咱们自界说的类
     const char *mangledName = cls->nonlaz源码本钱yMan实例化一个类gledName();
     const char *customerClassName = "JSPerson";
     if (strcmp(mangled实例化目标是什么意思Name, customerClassName) == 0) {
       //打印类名
       printf("%s -: no源码下载n-laz源码是什么意思y classes要研讨的类: - %sn",__func_变量是什么意思_,mangledName);
      }

     addClassTableEntry(cls);

     if (cls->isSwiftStable()变量名的命名规矩) {
       if源码 (cls->swiftMetadataInitializer()) {
         _objc_fatal("Swift class %s with a metadata init源码年代ializer "
               "is not al实例化类lowed to be non变量是什么意思-lazy",
               cls-源码之家>nameForLogging());
        }
       // fixm源码年代e alswiftlyso disallow relocatable classes
       // We canappreciate't disallswiftlyow all Swift classes because of
       // classes like Swift.__EmptyArrayStorage
      }
     realizeClas实例化类sWithoutSwift(cls, niswifterl);
    }
  }
 ts.log("IMAGE TIMES: realize non-lazy c源码下载lasses");
 // Realize newly-resolved future classes, i变量的界说n case CF manipulates them
 if (resolvedFutureClasses) {
   for (i = 0; i < rapp下载esolvedFutureClassCount; i++) {
     Class cls变量的界说 = resolvedFutureClasses[i];
     if (cls->isSwiftStable()) {
       _objc_fatal("Swiftappetite clswift国际结算体系ass is not allowed to be future");
      }
     ///调试代码 确定是咱们自界说的类
     const char *mangledName = cls源码是什么意思->nonlazyMangledNswiftcode是什么意思中文ame();
     const char *customerClassName = "JSPerson";
     if (strcmp(mswift怎样读angledName, customerClassName) == 0) {
       //打印类名
       printf("%s -: realize future classes要研讨的类: - %sn",__func__,mangledName);
      }
     realizeClassWit实例化类houtSwift(cls, nil);
     cls->setInstancesSwiftRequireRawIsaRecursively(false/*inherited*/);
    }
   free(resolvedFutureClasses);
  }
 ts.log("IMAGE TIMES: realize future classes");

在两行printf的当地打断变量泵点，作业源码程序，看是否实施到断点方位。发现打印了_read_images -:源码之家 non-lazy classes要研讨的类: - JSPerson，代码实施到了non-lazy classes,里面类加载的中心代码在realizeClassWithoutSwift函数，咱们持续根究realizeClassWithoutSwift函数。

realizeClassWithoutSwift剖析

操作之前的ro

咱们从上到下顺次阅读代码，定位到auto ro = (const class_ro_t )cls->data();,由于ro是clean Memory里的数据咱们比较活络，咱们在图示方位打断点：

运用LLDB调试程序，检查ro里的信息：

(lldb) p ro变量泵
(const class实例化是什么意思_ro_t *) $0 = 0x00000001000080c0
(lldb) p *$0
(const class_ro_t) $1 =实例化目标 {
flags = 0
instanceStaapp是什么意思rt = 8
insta实例化目标的关键字nceSize = 16
reserved = 0
 = {
 ivarLayout = 0x0000000000000000
 nonMetaclass = nil
}
name = {
 std::__1::atomicswiftcode代码查询<const char *> = "JSPerson" {
  Value = 0x0000000100003db0 "JSPerson"源码下载
  }
}
b源码a实例化需求seMethodList = 0x0000000100008108
baseProtoc源码怎样做成app软件ols = 0x0000000000000000
ivars = 0x0000000100008170
weakIvarswift怎样读Layout = 0x0000000000000000
baseProperties = 0x变量与函数0000000100008198
_swiftMetadataInitializer_NEVER_USE = {}
}
(lldb) p $1.baseMethodList
(void *constapple) $2 =变量 0x0000000100008108
(lldb) p *$2变量名的命名规矩
(lldb)

经过打印咱们发现此时ro里的baseMethodList为空，现在还不清楚什么时分赋值的，咱们application持续根究。

rw的赋approach值

接下来便是对rw的赋值app是什么意思，留意rw是dirty Memory

if (ro->flags & RO_FUTURE) {
  // This was a future class. rw data is already allo源码交易平台排行cated.
  rw = cls->data();
  ro = cls->data()-&gswift代码t;ro();
  ASSERT(!is变量名的命名规矩Meta);
  cls->changeInfo(RW_REALIZED|RW_REALIZING, RW_FUTURE);
} else {
  // Normal class. Allocat变量的界说e writeable class data.
  rw = objc::zalloc<class_rw_t>();
  rw->set_ro(ro);
  rw->flags = RW_REALIZED|RW_REALIZING|isMeta;
  cls-&gt变量之间的联系;setData(rw);
}

isa和su实例化目标有几种办法perClass赋值

后swiftly边的代码便是对isa和suswift怎样读perClass的赋值：

supercls = realizeClassWithoutSwift(remapClass(clswiftcode是什么意思中文s->getSuperclass()), nilapplication);
metacls = realizeClassWithoutSwift(remapClass(cls->ISA()), nil源码本钱);

#if SUPPORT_NONPOINTER_ISA
 if (isMeta) {
   // Metaclasses do not nswift代码eed any features from non pointer ISA
   // This allows f变量名or a faspath for classes iswift代码n objc_retain/objc_release.
   ///元类 不是nswiftlyon pointer ISA
   cls->setInstancesRequireRawIsa();
  } el实例化一个类se {
   // Disable non-poinswift代码ter isa for some classes and/or platfo源码之家rms.
   // Setappstore instancesRequir变量名eRawIsa.
   bool instancesRequireR变量名awIsa = cls->instancesRequireRawIsa();
   bool rawIsaIsInheriteappstored = false;
   static bool hackedDispatch = false;

   if (DisableNonpointerIsa) {
     //假设咱们设置变量不运用 non pointer ISA 也会是纯的isa
     // Non-pointer isa disabled变量的指针其意义是指该变量的 by eapproachnvironment or app SDK version
     instancesRequireRawIsa = true;
    }
   else if (!hackedDispatch && 0 == strcmp(ro-swift体系>getName(), "OS_object"))
    {
     // hack for libdis变量patch et al - isaappreciate also acts as vtable pointer
     hackedDispaAPPtch = true;
     instancesRequireRawIsa = true;
    }
   else if (suappstorepercls && supercapp是什么意思ls->getSuperclass() &&
        su实例化类percls-&g变量名t;instancesRequ实例化目标的关键字ireRawIsa())
    {
     // This is also propagated by addSubclass()
     // but nonpointer isa setup needs it earlier.
     // Special case: instancesRequireRawIsa does not propagate
     // from root class to root metaclass
     instappleancesRequireRawIsa = true;
     rawIsaIsInherited = true;
    }

   if (instancesRequireRawIsa) {
     cls->setInstancesappleRequappreciateireRawIsaRecursively(rawIsaIsInherited);
    }
  }
// SUPPORT_NONPOINTER源码之家_ISA
#endif
 // Updat源码编辑器e superclass answift怎样读d metaclass in case of rapp下载emapping
 cls->setSuperclass(supe实例化需求rcls);
 cls->swiftcode是什么意思中文initClassIsa(metacls);

在realizeClassWithoutSwift函数最终会调用methodizeClas实例化目标有几种办法s变量之间的联系,咱们下一小节根究methodizeClass。

methodizeClass剖析

methodizeClass断章取义便是源码怎样做成app软件对办法的处理。

static void metho变量dizeClass(Class cls, Cl源码年代坑人ass previously)
{
 runtimeLock.assertLocked();
 bool isMeta = cls->isMetaClass();
 auto rw = cls-&gt源码交易平台排行;data();
 auto ro = rw-&gappetitet;ro();
 auto rwe = rw->ext()源码下载;
 // Methodizing for the first time
 if (PrintConnectin实例化一个类g) {
   _objc_inform("CLASS: methodizing class '%s' %s",
          cls->nameForLog变量是什么意思ging(),swift代码 isMeta ? "(meta)" : "");
  }
 ///调试代码 确定是咱们自界说的类
 consSwiftt char *mangledName =swiftkey cls->nonlazyMangledName(swiftcode是什么意思中文);
 const char *customerClassName = "JSP变量泵ersonapp是什么意思";
 if (strcmp(mangledName, custo源码交易网站源码merClassName) == 0) {
   //打源码之家印类名
   if (!isMeta) {
     prin源码本钱tf("%s -: non-lazy classes要研讨的类: - %sn"源码年代坑人,app是什么意思__func__,mangledName);
    }
  }
 // Install methods and properties that the class implements itself.
 //取出办法列表
 method_list_t *list = ro->baseMethods();
 if (list变量名) {源码之家
   prepareMethodLappreciateists(cls, &list, 1, YES, isBundleClass(cls), nullptr);
   if (rwe) rwe-&g变量是什么意思t;methods变量类型有哪些.attachLists(变量类型有哪些&aapplemp;list, 1);
  }
 property_list_t *proplist = ro-&g源码怎样做成app软件t;baseProperties;
 if (r源码编辑器we && proplist) {
   rwe->propapplicationerties.变量的指针其意义是指该变量的attachLiSwiftsts(&proplist, 1);
  }
 protocol_list_t *protolist = ro->baseProtocols;
 if (rwe && protolist) {
   rw实例化一个类e->pro源码交易平台排行tocols.attachLists(&protolist, 1);
  }
 // Root classes get bonus method implementations if theyappreciate don't have
 // them already. These apply before category replacements.
 if (cls->isRootMetaclass()) {
   // roSwiftot metaclass
   addMethod(cls, @selector(initialize), (IMP)&objc_noop_imp, "", NO);
  }
 // Attaswiftcode代码查询ch categories.
 if (源码编辑器previously) {
   if (isMeta) {
     objc::unattachedCategories.attachToClass(cls, previously,
                          ATTACH_METACLASS);
    } else {
     // When a class relocates, categories with class methods
     // may be registered on the class itself rather than on
     // the metaclass. Tell attachToClass to look for those.
     objc::unattachedCategories.attachToCl实例化目标的关键字ass(cls, pappearreviously,
                          ATTACH_CLAswift怎样读SS_AND变量名_METACLASS)实例化需求;
    }
  }
 objc::unattachedCat源码之家egories.attachToClass(cls, cls,
                      isMeta ? ATTACH_METACLASS : ATTACH_appearCLASS);

#if DEBUG
 // Debug: sanity-check all SELs; log method list contents
 for (coswift国际结算体系nst auto& me实例化目标的关键字th : rw->me源码thods()) {
   if (源码年代坑人PrintConnecting) {
     _objc_inform("METHOD实例化类 %APPc[%s %s]", isMeta ? '+' : '-',
            cls->nameForLogging(), sel_getName(m变量类型有哪些eth.name()));
    }
   ASSERT(sel_swifterregisterName(sel_getNappleame(meth.name())) == meth.name(源码编辑器));
  }
#endif
}

断点进入图示方位，此时办法列表仍是不能源码是什么意思打印

prepareMethodLists

咱们持续根究，后边实施prepareMethodLisswiftlyts函数。

static void
prepareMethodLists(Class cls, method_list_t **addedLists, int addedCount,
         bool baseMethods, bool methodsFromBundle, const char *w源码编辑器hy)
{
 runtimeLock.assertLo变量的指针其意义是指该变量的cked();
 if (addedCount == 0) return;
 // There exist RR/AWZ/Core special cases fappointmentor some class's base methods.
 /变量之间的联系/ But this code should never need to scan base methods for RR/AWZ/Core:
 // default RR/AWZ/Core cannot be set before setInitialized().
 // Therefore源码本钱 we needAPP not handle any special case源码年代坑人s here.
 if (baseMethods) {
   ASSERT(cls->hasCustomAWZ() && cls->hasCuswifters变量值tomRR() && cls->hasCustomCore());
  } else if (cls->cache.isConstant实例化是什么意思OptimizedCac变量名he()) {
   cls-&swiftcode是什么意思中文gt;setDisallowPreoptCachesRecursively(why);
  } else if (cls->allowsPreoptInlinedSels()) {
#if CO变量NFIG_USE_PREOPT_CACHES
   SEL *sels = (SEL *)objc_opt_offsets[OBJC_OPT_INLINED_METHODS_START];
   SEL *sels_end = (SEL *)objc_opt_offsets[OB变量JC_OPT_INLINED_MapproachETHODS_END];
   if (method_list变量的指针其意义是指该变量的s_contains_any(addedLists, addedL源码ists + addedCount, sels, sels_end - sels)) {实例化数组
     cls->setDisallo变量泵wPreoptInlinedSelsRecursively(why);
    }
#endif
  }
 // Add method lists to array.
 // Reallocate un-fixed method lists.
 // Tapp下载he new methods are PREPENDED to the method list array.

 for (int i = 0; i < addedCount; i++) {
   method_list_t *mlist = addedLists[i];
   ASSERT(mlappearist);
   // Fixup selectors if necessary
   if (!mlist->isFixedUp()) {
     //中心代码
     fixupMethodList(mlist, methodsFswiftlyromBundle, true/*sort*/);
    }
  }

 // If the class is initialized,源码年代坑人 then scan for method implementations
 // tracked by the class's flags. If it's not initialized yet,
 // then objc_class::setInitialized() will take car源码是什么意思e of it.
 if (cls->isInitialized()) {
   objc::AWZScanner::scanAddedMe变量thodLists(cls, addedL变量类型有哪些ists, addedCount);
   objc::appleRRScanner::scanAddedMethodLists(cls, add实例化目标有几种办法edLists, addedCount);
   objc::CorswiftereScanner::sc变量泵anAddedMetho源码年代坑人dLists(cls, add实例化目标是什么意思edLists, addedCount);
  }
}

中心调用是fixupMethodList函数。

fapp是什么意思ixupMeappstorethodList

static void
fixupMethodLisappreciatet(method_list_t *mlist, bo源码之家ol bu实例化目标有几种办法ndleCopy, bool sort)
{
 runtimeLock.assertLocked();
 ASSERT(!mlist->isFixedUp());
 // fixme lock less in attachMethodLists ?
 // dyld3 may have already uniqued, but not sorted, the list
 if (!mlist->isUniqued()) {
   mutex_locker_t lock(selLock);
 
   // Unique selectors in list.
   for (auto&amp源码年代坑人; meth : *mlist) {
     const char *name = sel_cna源码之家me(meth.name());
     meth.setNa变量名的命名规矩me(sel_registerNameNoLock(name, bundleCopy));
    }
  }
 // Sort by sel变量名的命名规矩ector address.
 /源码交易网站源码/ Don't try to sort small lists, as they're immutable.
 // Don't try to sort big lists of nonstandard size, as stabswiftcode是什么意思中文le_sort
 // won'tapproach copy the entries properly源码之家.
 if (sort &&appointment !mlist->isSmallswift体系List() &&变量之间的联系 mlist->entsize() == method_t::bigSize) {
   method_t::So变量rtBySELAddress sorter;
   std::stable_sort(&mlist->begin()->bi实例化一个类g(), &mlist->end()->big(), sor变量之间的联系ter);
  }
 // Mark method list as uniqued and sorted.
 // Can't mark small lists, since they're immutableAPP.
 if (!mlist-&gt实例化类;isSmallList()) {
   mlist-&源码是什么意思gt;setFixedUp();
  }
}

中心的代码源码编辑器是stable_sort，咱们别离打印排序前后办法列表，如图示

留意：这儿一定要先在realizeClassWithoutSwift判别好是咱们要研讨的JSPerson类，然后再看打印效果，否则体系类也会有许多打印，影响咱们剖析。

me实例化thodizeClass -: non-lazy classes要研讨的类: - JSPerson
****************sort之前 : say1 - 0x100003dda
sort之前 : say2 - 0x100003ddf
sort之前 : nickNamappointmente - 0x7fff73fb8a1c
sort之前 : setNickName: - 0x7fff73fb8362
****************sort之后 : say1 - 0x1swift体系00003dda
sort之后实例化需求 : say2 - 0x100003ddf
sort之后 : setNickName: - 0x7fff73fb8362
sort之后 : nickName - 0x7fff73fb8a1c

经过上面打印效果：

排序前：say1appointment - 0x100003dda、say2 - 0x100003ddf、nickName - 0x7fff73fb8a1c、setNickName: - 0x7fff73fapp下载b8362
排序后：say1 - 0x100003ddaswift代码是什么意思、say2 - 0x100003ddf、setNickName: - 0x7fff73fb8362、nickName - 0x7fff73fb8a1c
排序是依实例化目标是什么意思据地址由低到高排序的。

小结

到现在为止，类的加载流程是：_read_im实例化数组ages->re实例化一个类alswift代码是什么意思izeClassWithoutSwiftapproach->methodizeClass->prepareMethodLists->fixupMethodL实例化目标ist。

懒加载类和非懒加载类

咱们前面根究的其实都是非懒加载的类，懒加载类和非懒加载的类的差异便是是否完成了load办法。

非懒加载

经过上面的剖析，咱们现已很清楚了，是在_objc_源码交易网站源码init办法里加载变量名的，也便是程序发起的时分APP。这也便是为什么变量之间的联系load办法过多，会影响咱们使用的发起速度。

懒加载类

由于非懒加载类效率低，会影响咱们的发起速度，那懒加载类是什么时分加载的呢？咱们删掉JSPerson类的load办法，然后在main函数中实例化一个JSPerson实例

in实例化servlet类异常t main(int arg源码编辑器c, const charapplication * argv[]源码年代坑人) {
@autorelea变量值sepool {
JSPerson *p = [JSPerson alloc];
[p say1]app下载;
NSLog(@"Hello, World!");
}
return 0;
}

咱们首先在main办法里增加断点，实施程序。走到main函数之swift代码是什么意思后，然后再在realizeClassWithoutSwift增加断点：

断点走进来之后咱们bt打印调用栈信息：

发现调用是从lookUpImpOrForward开端。

所以咱们的结论是懒加载的类是在第一次被运用的时分加载的。

总结

非懒加载类：程序作业时加载，_read_images->realizeClassWithoutSwift->metho实例化数组dizeClass->prepareMethodLists->fixupMethodList。
懒加载类：第一次运用时加载，lookUpImpOrForward->realizeClassWithoutSwift->变量与函数methodizeClass->prepareMethodLists->fixupMethodList

咱们开发中经常会写分类，它是什么时分加载的及加载的流程，咱们下一篇再根究。

iOS底层-类的加载（中）

realizeClass的引入

realizeClassWithoutSwift剖析

操作之前的ro

rw的赋approach值

isa和su实例化目标有几种办法perClass赋值

methodizeClass剖析

prepareMethodLists

fapp是什么意思ixupMeappstorethodList

小结

懒加载类和非懒加载类

非懒加载

懒加载类

总结

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