类、实例、状态

调试期间，类和实例的对比：

概述

• 普通的类的对象=类的实例是

  (lldb) reg r x0
        x0 = 0x0000000280f603f0
  (lldb) po 0x0000000280f603f0
  <UMUserManager: 0x280f603f0>
  

• 类本身是

  (lldb) reg r x0 x1
        x0 = 0x00000001db187788  (void *)0x002d8581db1877b0
        x1 = 0x00000001cc359b7e  
  (lldb) po 0x00000001db187788
  UMUserManager
  

详解

• 普通的：Instance=实例=对象=Object
  • 典型=多数情况
    • register read时：后面没有额外备注
      • 举例

        (lldb) reg r x0
        x0 = 0x000000010210eb50
        

    • po打印输出：类名加上地址
      • 举例
        • AAUISignInViewController的实例

          (lldb) po 0x000000010210eb50
          <AAUISignInViewController: 0x10210eb50>
          

          
        • UMUserManager的实例

          (lldb) po 0x0000000280f603f0
          <UMUserManager: 0x280f603f0>
          

    • -》对应后续函数调用，ObjC写法是：-开头
      • 举例
        • -[AAUISignInViewController _setEnabled: 0]
  • 少数=特殊情况
    • 已alloc，但还没init
      • 现象：po打印（内部调用类的description）时，会输出特殊的提示：object was not initialized

        (lldb) po 0x0000000281e79600
        *** -[NSURLComponents description]: <NSURLComponents 0x281e79600> object was not initialized
        

      • 后续会
        • 调用init去初始化
        • 最后才是，已初始化好的，普通的类的实例
          • po打印出description描述
• 特殊的：Class=类
  • register read时：后面会有备注
    • 举例

      (lldb) reg r x0
      x0 = 0x00000001dba36140 (void *)0x00698f81dba36118
      

      
  • po打印输出：只有类名，没有地址
    • 举例

      (lldb) po 0x00000001dba36140
      AAPersonaUtility
      

  • -》对应后续函数调用，ObjC写法是：+开头
    • 举例
      • +[AAPersonaUtility verifyAndFixPersonaIfNeeded: <UMUserPersona: 0x280d2b940> desiredContext: <UMUserPersonaContext: 0x281a30830>]

举例

已alloc，但还没init的实例

汇编代码:

    0x19447a1b0 <+152>: adrp   x8, 279478
    0x19447a1b4 <+156>: ldr    x0, [x8, #0xfa0]
    0x19447a1b8 <+160>: bl     0x199f71380              ; objc_alloc

->

(lldb) reg r x0
      x0 = 0x00000001db033b48  (void *)0x003a0101db033bc0
(lldb) po 0x003a0101db033bc0
16326656130235328

(lldb) po 0x00000001db033b48
NSURLComponents

运行后，返回值：

(lldb) reg r x0
      x0 = 0x0000000281e79600
(lldb) po 0x0000000281e79600
*** -[NSURLComponents description]: <NSURLComponents 0x281e79600> object was not initialized

以及后续会有对应：调用init函数去初始化

    0x19447a1bc <+164>: adrp   x8, 227332
    0x19447a1c0 <+168>: add    x1, x8, #0xcfe            ; =0xcfe 
    0x19447a1c4 <+172>: adrp   x2, 300159
    0x19447a1c8 <+176>: add    x2, x2, #0x7a0            ; =0x7a0 
    0x19447a1cc <+180>: bl     0x199f6d5c0              ; objc_msgSend

-》

(lldb) reg r x0 x1 x2
      x0 = 0x0000000281e79600
      x1 = 0x00000001cbc7ecfe  
      x2 = 0x00000001dd8f97a0  @"https://setup.icloud.com"
(lldb) po 0x0000000281e79600
*** -[NSURLComponents description]: <NSURLComponents 0x281e79600> object was not initialized

(lldb) po (char*)0x00000001cbc7ecfe
"initWithString:"

(lldb) po 0x00000001dd8f97a0
https://setup.icloud.com

即：

-[<NSURLComponents 0x281e79600> initWithString: @"https://setup.icloud.com"]

返回值=初始化后，就是：

普通的，已初始化好的类，po打印其description描述了：

(lldb) reg r x0
      x0 = 0x0000000281e79600
(lldb) po 0x0000000281e79600
<NSURLComponents 0x281e79600> {scheme = https, user = (null), password = (null), host = setup.icloud.com, port = (null), path = , query = (null), fragment = (null)}