Question

我已经被困在这一段时间了但是发生的事情是当请求从mysql返回时有一个空值但是我如何检查空值是否达到了我的条件以便我不存储这个值在数组中。代码在

之下

我一直得到的错误是 - [NSNull isEqualToString：]：无法识别并且我试图在tableview中绑定数组

- (void)viewDidLoad {

JobAddSiteAppDelegate *ja = (JobAddSiteAppDelegate *)[[UIApplication sharedApplication] delegate];

tempArray = [[NSMutableArray alloc] init];
NSString *strURL = [NSString stringWithFormat:@"http://www.bestitjobs.co.uk/appresults3.php", ""];
NSData *nsData = [NSData dataWithContentsOfURL:[NSURL URLWithString: strURL]];
//NSLog(@"JSON: %@", nsData);
//NSString *strResult = [[[NSString alloc] initWithData:nsData encoding:NSUTF8StringEncoding] autorelease];
//NSLog(@"Result: %@",strResult);

//NSError *e = nil;
JSONDecoder* decoder = [[JSONDecoder alloc] init];
NSDictionary* listDictionary = [nsData objectFromJSONData];
NSArray* people =[listDictionary objectForKey:@"jobs"];

for (NSDictionary *person in people) { 
    NSLog(@"people %@",people);
    if([person objectForKey:@"position"] != [NSNull class])
    { 
            NSString *position = [person objectForKey:@"position"];
            NSLog(@"position %@",position);
            [tempArray addObject: position];
    }
}
self.listData = tempArray;


[tempArray release];
[listData release];
[super viewDidLoad];

}

错误

2012-12-06 12：22：11.314 JobAddSite [7718：207]职位高级网络与系统顾问 2012-12-06 12：22：11.316 JobAddSite [7718：207]职位SAP Business One / SAP B1顾问伦敦 2012-12-06 12：22：11.317 JobAddSite [7718：207]职位业务发展经理 - 市场领先的IT公司 2012-12-06 12：22：11.318 JobAddSite [7718：207] - [NSNull isEqualToString：]：无法识别的选择器发送到实例0xe565e8 2012-12-06 12：22：11.321 JobAddSite [7718：207] *由于未捕获的异常'NSInvalidArgumentException'而终止应用程序，原因：' - [NSNull isEqualToString：]：无法识别的选择器发送到实例0xe565e8' * 在第一次投掷时调用堆栈：（ 0 CoreFoundation 0x00de95a9 exceptionPreprocess + 185 1 libobjc.A.dylib 0x00f3d313 objc_exception_throw + 44 2 CoreFoundation 0x00deb0bb - [NSObject（NSObject）doesNotRecognizeSelector：] + 187 3 CoreFoundation 0x00d5a966 __ 转发 + 966 4 CoreFoundation 0x00d5a522 _CF_forwarding_prep_0 + 50 5 JobAddSite 0x000024cd - [ResultViewController viewDidLoad] + 604 6 UIKit 0x00389089 - [UIViewController视图] + 179 7 UIKit 0x0038aa3d - [UIViewController viewControllerForRotation] + 63 8 UIKit 0x00386988 - [UIViewController _visibleView] + 90 9 UIKit 0x0062893c - [UIClientRotationContext initWithClient：toOrientation：duration：andWindow：] + 354 10 UIKit 0x0030081e - [UIWindow _setRotatableClient：toOrientation：updateStatusBar：duration：force：] + 954 11 UIKit 0x00588619 - [UIWindowController转换：fromViewController：toViewController：target：didEndSelector：] + 1381 12 UIKit 0x0038d65d - [UIViewController presentModalViewController：withTransition：] + 3478 13 JobAddSite 0x0000213f - [JobAddSiteViewController搜索] + 270 14 UIKit 0x002d94fd - [UIApplication sendAction：to：from：forEvent：] + 119 15 UIKit 0x00369799 - [UIControl sendAction：to：forEvent：] + 67 16 UIKit 0x0036bc2b - [UIControl（内部）_sendActionsForEvents：withEvent：] + 527 17 UIKit 0x0036a7d8 - [UIControl touchesEnded：withEvent：] + 458 18 UIKit 0x002fdded - [UIWindow _sendTouchesForEvent：] + 567 19 UIKit 0x002dec37 - [UIApplication sendEvent：] + 447 20 UIKit 0x002e3f2e _UIApplicationHandleEvent + 7576 21 GraphicsServices 0x01741992 PurpleEventCallback + 1550 22 CoreFoundation 0x00dca944 CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION + 52 23 CoreFoundation 0x00d2acf7 __CFRunLoopDoSource1 + 215 24 CoreFoundation 0x00d27f83 __CFRunLoopRun + 979 25 CoreFoundation 0x00d27840 CFRunLoopRunSpecific + 208 26 CoreFoundation 0x00d27761 CFRunLoopRunInMode + 97 27 GraphicsServices 0x017401c4 GSEventRunModal + 217 28 GraphicsServices 0x01740289 GSEventRun + 115 29 UIKit 0x002e7c93 UIApplicationMain + 1160 30 JobAddSite 0x00001dec main + 102 31 JobAddSite 0x00001d7d start + 53 ）抛出'NSException'实例后调用终止

Answer 1

试试这个：

if ([person objectForKey:@"position"]) {..}

这个是相同但可能更具可读性：

if ([person objectForKey:@"position"] != nil) {..}

Answer 2

您好使用以下代码。

工作得很好。

Download Supporting Files

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



SBJSON *parser = [[SBJSON alloc] init];


NSURLRequest *request1 = [NSURLRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:@"http://www.bestitjobs.co.uk/appresults3.php"]]];

NSLog(@"GGGG:%@",request1);


NSData *response1 = [NSURLConnection sendSynchronousRequest:request1 returningResponse:nil error:nil];



NSString *json_string = [[NSString alloc] initWithData:response1 encoding:NSUTF8StringEncoding];



NSDictionary *statuses = [parser objectWithString:json_string error:nil];


NSLog(@"List Dictionary:%@",statuses);
NSArray* people =[statuses objectForKey:@"jobs"];

for(NSDictionary *test in people)
{
    [empArray addObject:[test valueForKey:@"position"]];


}


NSLog(@"EMP ARRAY CATEGORY:%@",empArray);

注意：在使用SBJSon支持文件并导入JSON.h之前

并检查您的控制台。

Answer 3

检查这样的条件并向Array添加值

for (NSDictionary *person in people) { 
   NSLog(@"people %@",people);
   NSString *position = [person objectForKey:@"position"];
   if(position) {
      [tempArray addObject: position];
   }
}

objective c - 获取空值

3 个答案: