Question

Assuming the following example array:

{"/documents", "/documents/files", "/pictures"}

I wish to create a multidimensional NSMutableDictionary that looks like (if I were to create it manually):

NSArray *keys = [NSArray arrayWithObjects: @"documents", @"pictures", nil];
NSArray *objects = [NSArray arrayWithObjects: [NSDictionary dictionaryWithObject:[NSDictionary dictionary] forKey:@"files"], [NSDictionary dictionary], nil];

NSMutableDictionary *demoDict = [NSMutableDictionary dictionaryWithObjects:objects forKeys:keys];

NSLog(@"%@", demoDict);

Which would log as:

documents = {
    files = {
    };
};
pictures = {
};

How could I generate this automatically from a similar array with path lengths of an infinite length (so dictionaries of infinite dimensions?)

What I have so far (hopefully it’s useful as a starting point) is;
I put the comments of the logic above the code to make it easier on the eyes:
(_folderPaths is the array)

/**
 *set the root dictionary
 *iterate through the array
 *Split the path down by the separator
 *iterate over the path parts
 *make sure there is a part to the part, eliminates initial slash or
    double slashes
 *Check if key exists
 *if not then set a new mutdict for future children with key being the pathpart
**/

NSMutableDictionary *foldersDictionary = [NSMutableDictionary dictionary];


for(NSString *path in _folderPaths){

    NSArray *pathParts = [path componentsSeparatedByString:@"/"];

    for(NSString *pathPart in pathParts){

        if([pathPart length]>0)
        {
            if(![foldersDictionary objectForKey:pathPart])
                [foldersDictionary setObject:[NSMutableDictionary dictionary] forKey:pathPart];
            //Some way to set the new root to reference the Dictionary just created here so it can be easily added to on the next iteration?
        }

    } //end for pathPart in pathParts
} //end for path in _folderPaths

NSLog(@"%@", foldersDictionary);

This would log as:

documents = {
};
files = {
};
pictures = {
};

So I need a way of being able to step deeper into the dictionary with each iteration of the split path. I’ve done this before in C# on a node view where I could reference a child with a cursor but I’m not finding a way to do this with Objective-C using the pointers.

Answer 1

You’re pretty close. All you need to do is dynamically change the parent that new dictionaries get added to. You can do this like this:

NSMutableDictionary *folders = [NSMutableDictionary dictionary];

for (NSString *path in folderPaths) {
    NSMutableArray *folderStack = [NSMutableArray arrayWithObject:folders];

    for (NSString *component in [path pathComponents]) {
        if ([component isEqualToString:@"/"]) continue;

        NSMutableDictionary *folder = [[folderStack lastObject] objectForKey:component];
        if (folder == nil) {
            folder = [NSMutableDictionary dictionary];
            [[folderStack lastObject] setObject:folder forKey:component];
        }
        [folderStack addObject:folder];
    }
}

Note that under this method, these arrays would all yield the same result:

{"/documents", "/documents/pictures", "/documents/pictures/favorites"}
{"/documents/pictures/favorites", "/documents", "/documents/pictures"}
{"/documents/pictures/favorites"}