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OC-RunTime运行时技术的总结具体代码实现

2016-04-22 09:00 459 查看
<code class="hljs objectivec has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">RunTime简称运行时。就是系统在运行的时候的一些机制,其中最主要的是消息机制。对于C语言,函数的调用在编译的时候会决定调用哪个函数( C语言的函数调用请看这里 )。编译完成之后直接顺序执行,无任何二义性。OC的函数调用成为消息发送。属于动态调用过程。在编译的时候并不能决定真正调用哪个函数(事实证明,在编 译阶段,OC可以调用任何函数,即使这个函数并未实现,只要申明过就不会报错。而C语言在编译阶段就会报错)。只有在真正运行的时候才会根据函数的名称找 到对应的函数来调用。
下面主要来介绍下RunTime库所用到的几个函数:
+ (<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">BOOL</span>)resolveInstanceMethod:(SEL)sel
解释:这个函数在运行时(runtime),没有找到SEL的IML时就会执行。这个函数是给类利用class_addMethod添加函数的机会。具体实现如下:
+ (<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">BOOL</span>)resolveInstanceMethod:(SEL)sel
{
<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">NSLog</span>(@<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"2==%s %@"</span>,__func__,NSStringFromSelector(sel));

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//动态添加一个方法</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(sel == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">@selector</span>(run))
{
class_addMethod(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span>, sel, (IMP)Run, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"v@:"</span>);
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">YES</span>;
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> [<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span> resolveInstanceMethod:sel];
}
根据文档,如果实现了添加函数代码则返回<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">YES</span>,未实现返回<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">NO</span>。

+ (<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">BOOL</span>)resolveClassMethod:(SEL)sel

-(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">id</span>)forwardingTargetForSelector:(SEL)aSelector
解释:流程到了这里,系统给了个将这个SEL转给其他对象的机会。
返回参数是一个对象,如果这个对象非<span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">nil</span>、非<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span>的话,系统会将运行的消息转发给这个对象执行。否则,继续查找其他流程。

- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector
-解释:这个函数和后面的forwardInvocation:是最后一个寻找IML的机会。这个函数让重载方有机会抛出一个函数的签名,再由后面的forwardInvocation:去执行。

- (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span>)forwardInvocation:(NSInvocation *)anInvocation
解释:真正执行从methodSignatureForSelector:返回的NSMethodSignature。在这个函数里可以将NSInvocation多次转发到多个对象中,这也是这种方式灵活的地方。(forwardingTargetForSelector只能以Selector的形式转向一个对象)</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li></ul>


主要代码:
<code class="hljs objectivec has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#import <span class="hljs-title" style="box-sizing: border-box;">"Person.h"</span></span>

<span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">@implementation</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Person</span></span>
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//-(void)Run{</span>
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//    NSLog(@"xascdvdv");</span>
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//}</span>

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> Run(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">id</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span>, SEL sel)
{
<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">NSLog</span>(@<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"1==%@ %s 2"</span>,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span>, sel_getName(sel));
}

+ (<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">BOOL</span>)resolveInstanceMethod:(SEL)sel
{
<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">NSLog</span>(@<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"2==%s %@"</span>,__func__,NSStringFromSelector(sel));

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//动态添加一个方法</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(sel == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">@selector</span>(run))
{
class_addMethod(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span>, sel, (IMP)Run, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"v@:"</span>);
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">YES</span>;
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> [<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span> resolveInstanceMethod:sel];
}

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//当类的方法不存在时调用</span>
+ (<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">BOOL</span>)resolveClassMethod:(SEL)sel
{
<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">NSLog</span>(@<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"3===%s"</span>,__func__);

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> [<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span> resolveClassMethod:sel];
}
-(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">id</span>)forwardingTargetForSelector:(SEL)aSelector
{
<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">NSLog</span>(@<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"4==%s %@"</span>,__func__,NSStringFromSelector(aSelector));

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//转发给Animal的实例,调用Animal的Run方法,如果不转发则跳到Step 3</span>
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//    return [Animal new];</span>

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> [<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span> forwardingTargetForSelector:aSelector];
}
- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector
{
<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">NSLog</span>(@<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"5==%s %@"</span>,__func__,NSStringFromSelector(aSelector));

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(aSelector == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">@selector</span>(Run))
{
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> [NSMethodSignature signatureWithObjCTypes:<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"v@:"</span>];
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> [<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span> methodSignatureForSelector:aSelector];
}
- (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span>)forwardInvocation:(NSInvocation *)anInvocation
{
<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">NSLog</span>(@<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"6==%s"</span>,__func__);

SEL selector=[anInvocation selector];
Animal *animal=[Animal new];

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>([animal respondsToSelector:selector])
{
[anInvocation invokeWithTarget:animal];
}
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li><li style="box-sizing: border-box; padding: 0px 5px;">63</li><li style="box-sizing: border-box; padding: 0px 5px;">64</li><li style="box-sizing: border-box; padding: 0px 5px;">65</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li><li style="box-sizing: border-box; padding: 0px 5px;">63</li><li style="box-sizing: border-box; padding: 0px 5px;">64</li><li style="box-sizing: border-box; padding: 0px 5px;">65</li></ul>


运行结果:



代码Demo地址:http://pan.baidu.com/s/1bl8iCY

参考文章:

https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/ObjCRuntimeGuide/Introduction/Introduction.html#//apple_ref/doc/uid/TP40008048
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