看代码的时候看到一句，用于获取.plist文件的版本号

labelVersion.text = [NSString stringWithFormat:@"v%@", [[NSBundle mainBundle] objectForInfoDictionaryKey:(NSString*)kCFBundleVersionKey]];

比较感兴趣的是后面的参数 kcFBundleVersionKey ,竟然是CFBundle.h已经定于好的属性，下面有这个属性的注释

const CFStringRef kCFBundleVersionKey;

    /* The version number of the bundle.  For Mac OS 9 style version numbers (for example "2.5.3d5"), */

    /* clients can use CFBundleGetVersionNumber() instead of accessing this key directly since that */

    /* function will properly convert the version string into its compact integer representation. */

ios获取app版本号