ios判断应用是否在新版本下第一次调用某方法

+(BOOL)isFirstLaunch{
    static int cachedResult=-1;
    if (cachedResult!=-1) {
        return cachedResult;
    }
    NSString *appVersionKey=[NSString stringWithFormat:@"APP_VERSION_%@",[NSString getAppVersionString]];
    BOOL appVersionValue=[UserDefaultTool getBoolForKey:appVersionKey defaultValue:NO];
    cachedResult=!appVersionValue;
    [UserDefaultTool setBool:YES forKey:appVersionKey];
    return cachedResult;
}