NSString常量可以弱连接吗? [英] Can NSString constants be weak linked?
问题描述
NSString常量是否可以弱链接? AVCaptureSessionPresetiFrame960x540
未在iOS 5之前定义。我避免实际引用它并且它在gdb中加载正常,但是当我加载ipa时,它似乎在dyld之前崩溃调用main。
Can NSString constants be weak linked? AVCaptureSessionPresetiFrame960x540
isn't defined prior to iOS 5. I avoid actually referencing it and it loads fine in gdb, but when I load an ipa, it seems to crash in dyld before ever invoking main.
相关问题,使用弱链接框架的外部常量Crash ,似乎说不,我采用相同的方法:直接使用字符串值。
The related question, Using Weakly Linked Framework's extern constants Crash, seems to say "no" and I've taken the same apporoach: using the string value directly.
推荐答案
常量也可以弱连接。要测试常量是否可用,您必须在尝试使用它之前检查它的地址是否不是 NULL
:
Constants can be weak linked too. To test if the constant is available you must check if it’s address is not NULL
before you try to use it:
if (&AVCaptureSessionPresetiFrame960x540 != NULL) {
// Constant is available and can be used
}
请注意&
运算符以获取常量的地址。
Note the &
operator to take the address of the constant.
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