我在两个不同的VC中有一个prepareForSegue方法。一个使用 if 语句,而另一个使用开关。代码几乎完全相同,但名称除外。
I've got a prepareForSegue method in two different VCs. One uses an if statement, while the other is intended to use a switch. The code is virtually identical, except for names.
这个工作正常:
- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender { NSManagedObjectContext *localContext = [NSManagedObjectContext MR_contextForCurrentThread]; if ([[segue identifier] isEqualToString:@"addActivity"]) { UINavigationController *navController = (UINavigationController *)segue.destinationViewController; AddActivityViewController *aavc = (AddActivityViewController *)navController.topViewController; aavc.delegate = self; ListActivity *addedActivity = (ListActivity *)[ListActivity MR_createInContext:localContext]; aavc.thisActivity = addedActivity; }这个给了我两个警告。在第一行,我得到一个预期表达式警告。在第二行,我得到使用未声明的标识符'NavController'。
This one gives me two warnings. On the first line, I get an "Expected expression" warning. On the second line, I get "Use of undeclared identifier 'NavController'.
-(void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender { NSManagedObjectContext *localContext = [NSManagedObjectContext MR_contextForCurrentThread]; [SearchSpecs MR_truncateAllInContext:localContext]; [localContext MR_saveToPersistentStoreAndWait]; switch ([sender tag]) { case aVsAButton_tag: UINavigationController *navController = (UINavigationController *)segue.destinationViewController; AvsAViewController *aVSaVC = (AvsAViewController *)navController.topViewController; aVSaVC.delegate = self; SearchSpecs *thisSpec = (SearchSpecs *)[SearchSpecs MR_createInContext:localContext]; aVSaVC.currentSpec = thisSpec; break; default: break; } }有人可以指出我的错误吗?
Can someone please point out my mistake?
谢谢!
修改:
问题由所有给出的答案修正,并且非常感谢所有人!
The problem was fixed by all the answers given, and many thanks for all!
这是我的新代码:
-(void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender { NSManagedObjectContext *localContext = [NSManagedObjectContext MR_contextForCurrentThread]; [SearchSpecs MR_truncateAllInContext:localContext]; [localContext MR_saveToPersistentStoreAndWait]; switch ([sender tag]) { case aVsAButton_tag: { UINavigationController *navController = (UINavigationController *)segue.destinationViewController; AvsAViewController *aVSaVC = (AvsAViewController *)navController.topViewController; aVSaVC.delegate = self; SearchSpecs *thisSpec = (SearchSpecs *)[SearchSpecs MR_createInContext:localContext]; aVSaVC.currentSpec = thisSpec; } break; default: break; } }当我添加分号时根据第三个答案的建议,我在默认值行收到了Switch case in protected scope的警告。但是,当我将 case 代码括在大括号中时,所有问题都会消失。我记得很好的事情!
When I added the semi-colon per the suggestion of the third answer, I got the warning that "Switch case is in protected scope" at the default: line. However, when I enclosed the case code in curly brackets, all problems evaporated. Very good thing for me to remember!
我会检查所有的答案,但由于它们都是同时到达的,所以如果我接受,我希望没有人会被冒犯最佳。为所有人+1,再次感谢!
I would green-check all answers, but since they all arrived about simultaneously, I hope no one will be offended if I accept the top one. +1 for all, and thanks again!
推荐答案在C / Objective-C中,你不能在switch语句中声明变量那。如果要声明变量以用于switch语句的特定情况,可以将该案例的所有代码放在语句块中:
In C/Objective-C, you cannot declare variables in a switch statement like that. If you want to declare variables for use in a specific case of a switch statement, you can put all the code for that case in a statement block:
switch ([sender tag]) { case aVsAButton_tag: { UINavigationController *navController = (UINavigationController *)segue.destinationViewController; AvsAViewController *aVSaVC = (AvsAViewController *)navController.topViewController; aVSaVC.delegate = self; SearchSpecs *thisSpec = (SearchSpecs *)[SearchSpecs MR_createInContext:localContext]; aVSaVC.currentSpec = thisSpec; } break; default: break; }更多推荐
PrepareForSegue之谜
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