最近我们的 iOS APP 遇到较多闪退的问题，崩溃在 xls 解析相关代码，经过分析应该是使用的解析库 DHLibxls/DHxlsReader 内部的问题。

I believe you can always find a lot of this kind of Crash: Can't add self as subview.

We also know that we will never write code like add self as subview.

In fact, in most cases, the push and pop pages with animation and no animation occur at the same time.

Because we all know that this is often caused by the complexity of the page hierarchy and the unpredictable page jumps. So often choose to shelve this Crash helplessly.

But we always think about how to eliminate this Crash. Whether it is from the perspective of user experience or from the aspect of Crash rate management.

We all know that it is generally recommended to do simple cleanup in the dealloc method.

A very important reason is that in the process of destroying an object, if an operation such as weak is performed, it will cause a crash.

在公司的时候，通常 Crash 平台都做的很好，帮我们做好了符号化解析，一些三方平台也会提供类似的能力。

但我们还是会遇到需要自己做符号化解析的场景，比如某些线下包没有解析成功，又比如离开了公司提供的环境的时候等等。

所以我们还是有必要了解如何做符号化解析。