Question

我正在尝试检索id的价值：

{"id":1,"name":"XYZ"}

当我使用时：

NSString *jsonData = [[NSString alloc] initWithContentsOfURL:[NSURL URLWithString:url]];
NSArray * myPeople = [jsonData JSONValue]; 

NSString *name = [[NSString alloc] init]; 
NSDictionary *person = [myPeople objectAtIndex:[indexPath row]]; 
name = [NSString stringWithString:[person valueForKey:@"id"]]; 
name = [name stringByAppendingString:@". "]; 
name = [name stringByAppendingString:[person valueForKey:@"name"]]; 
name = [name stringByAppendingString:[person valueForKey:@"id"]]; 

cell.textLabel.text = name;

我收到以下错误：

*** Terminating app due to uncaught exception 'NSInvalidArgumentException'
reason: '-[NSCFNumber length]: unrecognized selector sent to instance 0x4e7f8b0

我该如何解决这个问题？

Answer 1

您同时拨打stringWithString:和stringByAppendingString:，但随后传入NSNumber

您需要获取NSNumber

的字符串值

[[person valueForKey:@"id"] stringValue];

或使用如下格式：

name = [NSString stringWithFormat:@"%@%@", name, [person valueForKey:@"id"]];

我还会考虑稍微改变结构，以便更容易遵循：

NSDictionary *person = [myPeople objectAtIndex:[indexPath row]];
NSString *personName = [person valueForKey:@"name"];
NSSNumber *personId  = [person valueForKey:@"id"];

NSString *name = [NSString stringWithFormat:@"%@. %@ %@", personId, personName, personId];

对于排序，您希望确保每次设置单元格时都不会提取数据（看起来像你），否则这将是一次糟糕的体验。

我相信有人可以指出你更好的排序方式，但我能想到的最快的事情是

NSArray *myPeople = [[jsonData JSONValue] sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
  return [[obj1 objectForKey:@"id"] compare:[obj2 objectForKey:@"id"]];
}]

使用从JSON数据中提取的值时的NSInvalidArgumentException

1 个答案: