objective c - Plist Array to NSDictionary

Question

I have a plist:

<plist version="1.0">
  <array>
    <dict>
      <key>name</key>
      <string>Alabama</string>
      <key>abreviation</key>
      <string>AL</string>
      <key>date</key>
      <string>1819</string>
      <key>population</key>
      <string>4,627,851</string>
      <key>capital</key>
      <string>Montgomery</string>
      <key>largestCity</key>
      <string>Birmingham</string>
    </dict>
    <dict>
      <key>name</key>
      <string>Alaska</string>
      <key>abreviation</key>
      <string>AK</string>
      <key>date</key>
      <string>1959</string>
      <key>population</key>
      <string>683,478</string>
      <key>capital</key>
      <string>Juneau</string>
      <key>largestCity</key>
      <string>Anchorage</string>
    </dict>
    ...
  </array>
</plist>

I am trying to load it into an NSDictionary like this:

NSString *path = [[NSBundle mainBundle] pathForResource:@"stateInfo" ofType:@"plist"];

NSFileManager *fileManager = [NSFileManager defaultManager];
if ([fileManager fileExistsAtPath:path]) {
    NSLog(@"The file exists");
} else {
    NSLog(@"The file does not exist");
}

NSMutableDictionary *myDic = [[NSMutableDictionary alloc] initWithContentsOfFile:path];
//NSDictionary *myDic = [NSDictionary dictionaryWithContentsOfFile:path];
NSLog(@"The count: %i", [myDic count]);

NSArray *thisArray = [[NSArray alloc] initWithContentsOfFile:path];
NSLog(@"The array count: %i", [thisArray count]);

I always get an array count of 50 but a dictionary count of zero. So I tried looping through the array and adding it to the dictionary:

NSDictionary *eachState;
for (eachState in thisArray) {
    State *thisState = [[State alloc] initWithDictionary:eachState];
    [myDic setObject:thisState forKey:thisState.name];
}

But the loop is throwing an exception:

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '*** -[NSCFDictionary setObject:forKey:]: mutating method sent to immutable object'

State is a class with properties matching my plist. What am I doing wrong? I see all kinds of related questions out here but I can't get it.

Answer 1

The two problems:

• Loading the plist into an NSDictionary:

This is a simple problem, which it seems you have already figured out. The global object in your plist is an array, not a dict, so when you load it into the dictionary, it doesn't know what to do (incompatable types), so you're getting an empty dictionary.

• Looping through the array of dictionaries:

From the Exception you're getting, you are calling 'setObject:forKey:' on the dictionary, which is initialized as an NSDictionary, not an NSMutableDictionary. The pointer is typed as NSMutableDictionary, but not the actual in memory object. You need to change your line from.

NSMutableDictionary *myDic = [[NSDictionary alloc] initWithContentsOfFile:path];

to

NSMutableDictionary *myDic = [[NSMutableDictionary alloc] initWithContentsOfFile:path];

and actually, since loading the dictionary from the file gives you an empty dictionary, you are wasting cycles trying to load it from the file, and should just create a new one:

NSMutableDictionary *myDic = [[NSMutableDictionary alloc] init];