NSDictionary. How do I create directly from aformated file?

Question

This is a fairly trivial data parsing question. I'm just unclear on the methods I should be using to pull it off.

I've got a plain text file of a few hundred lines. Each line is of exactly the same format. The lines are in contiguous chunks where the first item in a line is essentially a key that is repeated for each line in a chunk:

key0
key0
key0

...

keyN
keyN
keyN

I would like to construct an NSDictionarys directly from this file where the lines for a given key are collapsed into a dictionary. So a dictionary of dictionarys.

Any thoughts on how to do this?

Cheers, Doug

UPDATE 0 - Here's a snapshot of the actual data Here is the actual data. I can dice the file into chunks for each chr? if need be. I'm happy with a solution that ingests a single chr.

chr1 0 2300000 p36.33 gneg

chr1 2300000 5300000 p36.32 gpos25

chr1 5300000 7100000 p36.31 gneg

chr1 7100000 9200000 p36.23 gpos25

// ... // lots more // ...

chrN 144700000 148400000 q22.3 gpos100

chrN 148400000 149600000 q23.1 gneg

chrN 149600000 150300000 q23.2 gpos25

chrN 150300000 154600000 q23.3 gneg

UPDATE 1 - The File is on disk In case I didn't make it clear, the data is on disk not memory resident. I actually think I could get away with dicing the file into pieces, one for each chr. I can then ingest into an NSArray and then on into an NSDictionary. Unless of course, someone has something snazzier.

Answer 1

Take a look at the NSScanner class.

Answer 2

The following solution provides a dictionary of arrays, but you can use it as a basis for producing any data structure you like:

// The values on each line are tab-delimited
NSString* data = @""
  "key1 a b"
  "key1 c d"
  "key2 e f"
  "key2 g h";

NSMutableDictionary* result = [NSMutableDictionary dictionary];  
NSArray* lines = [data componentsSeparatedByString:@"\n"];

for (NSString* line in lines) {
  NSArray* value = [line componentsSeparatedByString:@"\t"];
  NSString* key = [components objectWithIndex:0];
  [value removeObjectAtIndex:0]; // remove the key

  NSArray* currentValue = [result objectForKey:key];
  if (currentValue) {
    [currentValue addObjectsFromArray:value];
  } else {
    [result setObject:[value mutableCopy] forKey:key];
  }
}

/*

The result looks something like this:

{
  "key1": [
    ["a", "b"],
    ["c", "d"]
  ],
  "key2": [
    ["e", "f"],
    ["g", "h"]
  ]
}

*/