当访问NSMutableArray计数ios时应用程序崩溃

Question

我登陆到一个奇怪的问题，我无法使用array.count，崩溃我的应用程序。

@interface LAMasterViewController() 

NSMutableArray * claimReports 

@end 
    -(void) ViewDidLoad 
    { 
     claimReports = [[NSMutableArray alloc] init]; 
     [claimReports addObjectsFromArray:[[LADataModelController getSingleton] getClaimReportsOrderedByIncidentDate] ]; 

    } 

-(NSArray *) getClaimReportsOrderedByIncidentDate 
{ // it returns one record 
    NSManagedObjectContext *context = [self managedObjectContext]; 
    NSError *error; 
    NSFetchRequest *request = [[NSFetchRequest alloc] init]; 
    NSEntityDescription *entity = [ NSEntityDescription entityForName:@"ClaimReport" inManagedObjectContext:context]; 
    NSSortDescriptor *sortByIncidentDate = [[NSSortDescriptor alloc] initWithKey:@"dateOfIncident" ascending:NO]; 
    [request setEntity:entity]; 
    [request setSortDescriptors: [NSArray arrayWithObject: sortByIncidentDate]]; 

    NSArray *array = [context executeFetchRequest:request error:&error]; 
    NSLog(@"Array Count %i" ,array.count); 
    return array; 
} 


- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section 
{ 

    return claimReports.count; //crashes here 

} 

error: -[LSClaimReport count]: unrecognized selector sent to instance 0xa54afc0 2014-04-01 14:56:29.022 LossAdjusting[6956:70b] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[LSClaimReport count]: unrecognized selector sent to instance 0xa54afc0'

什么我错过了这里。看起来很愚蠢。请指导。 谢谢

Answer 1

长篇小说，你正在对待LSClaimReport的实例，就好像它是一个NSMutableArray实例。

结束。

编辑好的，flippany放在一边，你对实例变量和局部变量感到困惑，并且混淆了你的一个实例变量的类型。

在ViewDidLoad（情况下不正确，所以如果这是逐字复制，然后它甚至不会被调用），您引用的claimReports本地版本被创建，然后扔掉：

-(void)ViewDidLoad 
{ 
    NSMutableArray *claimReports = [[NSMutableArray alloc] init]; 
    [claimReports addObjectsFromArray:[[LADataModelController getSingleton] getClaimReportsOrderedByIncidentDate] ]; 
} 

，以后你参考实例变量版本：

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section 
{ 
    return claimReports.count; //crashes here 
} 

这显然是一个LSClaimReport实例，而不是一个NSMutableArray。

所以它看起来像：

1. 你已经宣布你@interface错误的类型。
2. 您没有正确初始化它（您已经修复了这一点）。

Answer 2

请删除本地Arraydeclaration：

NSMutableArray * claimReports = [[NSMutableArray alloc] init]; 

改用：

claimReports = [[NSMutableArray alloc] init]; 

如果这是没有类变量是，它添加到您@接口声明：

@interface LAMasterViewController() 
{ 
    NSMutableArray * claimReports 
} 
@end 

@implementation LAMasterViewController 

Answer 3

写在你的.h文件中

NSMutableArray * claimReports; 

，并在您的.m

-(void)viewDidLoad{ 
       claimReports = [[NSMutableArray alloc] init]; 
      [claimReports addObjectsFromArray:[[LADataModelController getSingleton] getClaimReportsOrderedByIncidentDate] ]; 
       } 

Answer 4

你有几件事情错了你的代码，清理起来将有助于解决这个问题，主要问题'-[LSClaimReport count]: unrecognized selector sent to instance 0xa54afc0'是因为你的实例调用count的LSClaimReport显然不应该发生。您的代码似乎认为claimReports是LSClaimReport的实例，而不是NSMutableArray的实例。

至于你的代码可能我建议更改为（请参见代码标注问题的意见）

@interface LAMasterViewController() 

// Clearly you want this as a private property so why would you want to change 
// to having this in the .h file which would make it public 
// But Issue 1 is here you are missing the semi-colon (`;`) of the end. 
@property (nonatomic, strong) NSMutableArray *claimReports; 

@end 

// Issue two you are missing the `@implementation LAMasterViewController` 
@implementation LAMasterViewController 

// The synthesize is done automatically so getters/setters/ivar are created automatically 

// Issue 3: ViewDidLoad isn't a valid selector so ViewDidLoad will never be called 
// It is viewDidLoad 
-(void)viewDidLoad 
{ 
    [super viewDidLoad]; // Issue 4: you missed the call to super 
    claimReports = [[NSMutableArray alloc] init]; 
    [claimReports addObjectsFromArray:[[LADataModelController getSingleton] getClaimReportsOrderedByIncidentDate]]; 

} 

-(NSArray *)getClaimReportsOrderedByIncidentDate 
{ // it returns one record 
    NSManagedObjectContext *context = [self managedObjectContext]; 
    NSError *error; 
    NSFetchRequest *request = [[NSFetchRequest alloc] init]; 
    NSEntityDescription *entity = [ NSEntityDescription entityForName:@"ClaimReport" inManagedObjectContext:context]; 
    NSSortDescriptor *sortByIncidentDate = [[NSSortDescriptor alloc] initWithKey:@"dateOfIncident" ascending:NO]; 
    [request setEntity:entity]; 
    [request setSortDescriptors: [NSArray arrayWithObject: sortByIncidentDate]]; 

    NSArray *array = [context executeFetchRequest:request error:&error]; 
    NSLog(@"Array Count %i" ,array.count); 
    return array; 
} 


- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section 
{ 

    return claimReports.count; 

} 

@end