iOS - 由于未捕获的异常'NSInvalidArgumentException'而终止应用程序

Question

So I am really new at developing for iOS, and I've been doing my best, to search for an answer, to debug it and anything I could come up with.

Though, I haven't been able to find a solution to the issue.

I've been trying to fetch an external JSON document, which works fine, but when it comes to parsing it, it buggers up.

First of all, this is the error message I'm getting, the whole lot of it.

2013-01-31 22:40:19.261 demodh[6205:c07] View Loaded
2013-01-31 22:40:19.479 demodh[6205:c07] -[__NSCFStringcountByEnumeratingWithState:objects:count:]: unrecognized selector sent to instance 0x7554f90 
2013-01-31 22:40:19.480 demodh[6205:c07] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFString countByEnumeratingWithState:objects:count:]: unrecognized selector sent to instance 0x7554f90'
*** First throw call stack:
(0x1c93012 0x10d0e7e 0x1d1e4bd 0x1c82bbc 0x1c8294e 0x28d3 0xbd6589 0xbd4652 0xbd589a 0xbd460d 0xbd4785 0xb21a68 0x4615911 0x4614bb3 0x4652cda 0x1c358fd 0x465335c 0x46532d5 0x453d250 0x1c16f3f 0x1c1696f 0x1c39734 0x1c38f44 0x1c38e1b 0x1bed7e3 0x1bed668 0x14ffc 0x1d6d 0x1c95 0x1)
libc++abi.dylib: terminate called throwing an exception
(lldb) 

And this is the code I'm using at the moment:

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSDictionary *allDataDictionary = [NSJSONSerialization JSONObjectWithData:webData options:0 error:nil];

    for(NSDictionary *dict in allDataDictionary)
    {
        if (![allDataDictionary isKindOfClass:[NSDictionary class]])
        {
            NSLog(@"2Unable to process temp array because it's an instance of %@", [allDataDictionary class]);
        }
        else
        {
            for(NSDictionary *deal in dict)
            {
                if (![deal isKindOfClass:[NSDictionary class]])
                {
                    NSLog(@"Unable to process temp array because it's an instance of %@", [deal class]);
                }
                else
                {
                    NSString *title = [deal objectForKey:@"title"];
                    NSLog(title);
                }
            }
        }

    }
}

And the JSON I'm loading is: Link

I hope you're able to assist me in finding a solution.

Answer 1

The problem is you're fast-enumerating a NSDictionary and expecting to get its values, when in fact you'll get its keys. When you try to fast-enumerate an NSString you get the assertion you're seeing. You probably wanted this:

for(NSObject *key in allDataDictionary) {
    NSDictionary *dict = allDataDictionary[key];
    ...
    for (NSObject *dealKey in dict) {
         NSDictionary *deal = dict[dealKey];
    }
    ...

Alternatively, if you really want to enumerate the values and don't need the keys:

for(NSDictionary *dict in [allDataDictionary allValues]) {
    ...