https://cubegao.com/tags/isa/ Recent content in Isa on cubegao Hugo zh-CN Thu, 03 May 2018 12:43:00 +0800 https://cubegao.com/post/2018-05-03-isa-rc/ Thu, 03 May 2018 12:43:00 +0800 https://cubegao.com/post/2018-05-03-isa-rc/ <p>大家都知道内存管理是通过引用计数管理对象的生命周期。</p> <p>那<code>isa</code>和引用计数又有什么关系呢？先留着疑问。</p> <p>###isa指针</p> <div class="goat svg-container "> <svg xmlns="http://www.w3.org/2000/svg" font-family="Menlo,Lucida Console,monospace" viewBox="0 0 456 169" > <g transform='translate(8,16)'> <path d='M -4,8 L -4,24' fill='none' stroke='currentColor'></path> <path d='M 4,8 L -4,40' fill='none' stroke='currentColor'></path> <path d='M 16,0 L 0,48' fill='none' stroke='currentColor'></path> <path d='M 4,56 L 12,40' fill='none' stroke='currentColor'></path> <path d='M 12,56 L 20,40' fill='none' stroke='currentColor'></path> <path d='M -4,136 L 4,120' fill='none' stroke='currentColor'></path> <path d='M 4,136 L 12,120' fill='none' stroke='currentColor'></path> <path d='M 12,136 L 20,120' 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style='font-size:1em'>c</text> <text text-anchor='middle' x='280' y='4' fill='currentColor' style='font-size:1em'>a</text> <text text-anchor='middle' x='280' y='52' fill='currentColor' style='font-size:1em'>s</text> <text text-anchor='middle' x='280' y='84' fill='currentColor' style='font-size:1em'>Y</text> <text text-anchor='middle' x='280' y='132' fill='currentColor' style='font-size:1em'>l</text> <text text-anchor='middle' x='288' y='4' fill='currentColor' style='font-size:1em'>n</text> <text text-anchor='middle' x='288' y='52' fill='currentColor' style='font-size:1em'>s</text> <text text-anchor='middle' x='288' y='84' fill='currentColor' style='font-size:1em'>;</text> <text text-anchor='middle' x='288' y='132' fill='currentColor' style='font-size:1em'>a</text> <text text-anchor='middle' x='296' y='52' fill='currentColor' style='font-size:1em'>.</text> <text text-anchor='middle' x='296' y='132' fill='currentColor' style='font-size:1em'>s</text> <text text-anchor='middle' x='304' y='4' fill='currentColor' style='font-size:1em'>O</text> <text text-anchor='middle' x='304' y='132' fill='currentColor' style='font-size:1em'>s</text> <text text-anchor='middle' x='312' y='4' fill='currentColor' style='font-size:1em'>b</text> <text text-anchor='middle' x='312' y='132' fill='currentColor' style='font-size:1em'>.</text> <text text-anchor='middle' x='320' y='4' fill='currentColor' style='font-size:1em'>j</text> <text text-anchor='middle' x='328' y='4' fill='currentColor' style='font-size:1em'>e</text> <text text-anchor='middle' x='336' y='4' fill='currentColor' style='font-size:1em'>c</text> <text text-anchor='middle' x='344' y='4' fill='currentColor' style='font-size:1em'>t</text> <text text-anchor='middle' x='352' y='4' fill='currentColor' style='font-size:1em'>i</text> <text text-anchor='middle' x='360' y='4' fill='currentColor' style='font-size:1em'>v</text> <text text-anchor='middle' x='368' y='4' fill='currentColor' style='font-size:1em'>e</text> <text text-anchor='middle' x='376' y='4' fill='currentColor' style='font-size:1em'>-</text> <text text-anchor='middle' x='384' y='4' fill='currentColor' style='font-size:1em'>C</text> <text text-anchor='middle' x='400' y='4' fill='currentColor' style='font-size:1em'>c</text> <text text-anchor='middle' x='408' y='4' fill='currentColor' style='font-size:1em'>l</text> <text text-anchor='middle' x='416' y='4' fill='currentColor' style='font-size:1em'>a</text> <text text-anchor='middle' x='424' y='4' fill='currentColor' style='font-size:1em'>s</text> <text text-anchor='middle' x='432' y='4' fill='currentColor' style='font-size:1em'>s</text> <text text-anchor='middle' x='440' y='4' fill='currentColor' style='font-size:1em'>.</text> </g> </svg> </div> <p>通过注释和代码不难发现，我们创建的一个对象或实例其实就是一个<code>struct objc_object</code>结构体。</p>