蘋果官方文檔寫的比較清楚：
NSAssert
Generates an assertion if a given condition is false.
Declaration
#define NSAssert(condition, desc, ...)
Parameters
condition：An expression that evaluates to YES or NO
desc： An NSString object that contains a printf-style string containing an error message describing the failure condition and placeholders for the arguments
...：The arguments displayed in the desc string
Discussion
The NSAssert macro evaluates the condition and serves as a front end to the assertion handler.
Each thread has its own assertion handler, which is an object of class NSAssertionHandler. When invoked, an assertion handler prints an error message that includes the method and class names (or the function name). It then raises an NSInternalInconsistencyException exception. If condition evaluates to NO, the macro invokes handleFailureInMethod:object:file:lineNumber:description: on the assertion handler for the current thread, passing desc as the description string.
This macro should be used only within Objective-C methods.
Assertions are disabled if the preprocessor macro NS_BLOCK_ASSERTIONS is defined.
而且在NSException.h 文件中，我們可以清楚的看到 NSAssert 的宏定義:
#define NSAssert(condition, desc, ...) \
do { \
__PRAGMA_PUSH_NO_EXTRA_ARG_WARNINGS \
if (!(condition)) { \
NSString *__assert_file__ = [NSString stringWithUTF8String:__FILE__]; \
__assert_file__ = __assert_file__ ? __assert_file__ : @"<Unknown File>"; \
[[NSAssertionHandler currentHandler] handleFailureInMethod:_cmd \
object:self file:__assert_file__ \
lineNumber:__LINE__ description:(desc), ##__VA_ARGS__]; \
} \
__PRAGMA_POP_NO_EXTRA_ARG_WARNINGS \
} while(0)
蘋果文檔提供了一種禁用Assertions的方法，在實踐的過程中我又發(fā)現(xiàn)了另外一個禁用NSAssert的方法，詳情如下：
- 蘋果文檔：“Build Settings” -> "preprocessor macro" -> 添加“NS_BLOCK_ASSERTIONS” 則禁用了Assertions
- 另一種方式：“Build Settings” -> "Other C Flags" -> 添加“-DNS_BLOCK_ASSERTIONS”即可
