警告：从不同的Objective-C类型分配

Question

我已经查看过虽然以前的问题和对这个错误的答案，但我无法弄清楚我做错了什么。谁能帮忙？

@synthesize myScrollView; 
@synthesize mathsPracticeTextArray; 

-(void)loadText 
{ 
    NSBundle *bundle = [NSBundle mainBundle]; 
    NSString *textFilePath = [bundle pathForResource:@"mathspractice" ofType:@"txt"]; 
    NSString *fileContents = [NSString stringWithContentsOfFile:textFilePath]; 
    mathsPracticeTextArray = fileContents; 

} 

- (void)viewDidLoad { 

    [super viewDidLoad]; 

    myScrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, 320, 480)]; 
    myScrollView.contentSize = CGSizeMake(320, 960); 
    myScrollView.pagingEnabled = FALSE;  
    myScrollView.scrollEnabled = TRUE; 
    myScrollView.backgroundColor = [UIColor whiteColor]; 

    *[self.view addSubview:myScrollView]; 
    UILabel *myLabel = [[UILabel alloc] initWithFrame:CGRectMake(0,100,960,40)]; 
    myLabel.text = [mathsPracticeTextArray componentsJoinedByString:@" "]; 
    [myScrollView addSubview:myLabel]; 
    [myLabel release];* 
} 

- (void)didReceiveMemoryWarning { 

    [super didReceiveMemoryWarning]; 

} 

- (void)viewDidUnload { 
} 


- (void)dealloc { 

    [myScrollView release]; 
    [mathsPracticeTextArray release]; 
    [super dealloc]; 

} 

@end 

Answer 1

我猜mathsPracticeTextArray被声明为NSArray*或NSMutableArray*，在这种情况下分配一个NSString*它（在-(void)loadText发生）会导致你在标题中提到的警告。

警告是一个线索发生了什么事情：NSString与NSArray不同，你不能把其中一个当作另一个。当您将错误类型的对象分配给变量时，您发送给对象的许多消息无法处理，您的应用程序将失败。