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Heap and Stack

Value types are created on the stack, Reference types are created on the heap.
Stack is attached to a thread, and Heap is attached to the application.
Stack is faster than Heap.

dealloc 是否需要调用[super dealloc]

ARC中不能调用[super dealloc]

MRC中,必须最后调用[super dealloc]

set a breakpoint in malloc_error_break to debug

The error message indicates a pointer to a block of freed memory doesn’t actually point to free memory. The most likely cause is that the memory is a freed object instance, but your code as an unretained reference to it and has tried to use it like a “live” instance.
Click on the breakpoints navigator (looks like a sign post) on the top of the left bar on XCode.
On the bottom left hand corner there is a plus sign. Click on it.
Add Symbolic Breakpoint and set malloc_error_break as the symbol.
Click the next breakpoint button.


Whenever you encounter EXC_BAD_ACCESS, it means that you are sending a message to an object that has already been released.
In summary, when you run into EXC_BAD_ACCESS, it means that you try to send a message to a block of memory that can’t execute that message.
Put differently, deallocated objects are kept alive for debugging purposes. If you send a message to a zombie object, your application will still crash as a result of EXC_BAD_ACCESS.
Click the active scheme in the top left and choose Edit Scheme.
Select Run on the left and open the Diagnostics tab at the top. To enable zombie objects, tick the checkbox labeled Enable Zombie Objects.

dyld: Library not loaded

In the target’s General tab, there is an Embedded Binaries field. When you add the framework there the crash is resolved.

Reference is here on Apple Developer Forums.


1. 下载安装Atom。 2. Atom -> Preferences -> Packages -> plantuml-viewer。 3. 学习语法,编写代码,自动生成对应图形。