Sort array into dictionary - iphone

Question

I have and array of many strings.
I wan't to sort them into a dictionary, so all strings starting the same letter go into one array and then the array becomes the value for a key; the key would be the letter with which all the words in it's value's array begin.
Example
Key = "A" >> Value = "array = apple, animal, alphabet, abc ..."
Key = "B" >> Value = "array = bat, ball, banana ..."
How can I do that?
Thanks a lot in advance!

Answer 1

NSArray *list = [NSArray arrayWithObjects:#"apple, animal, bat, ball", nil];
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
for (NSString *word in list) {
NSString *firstLetter = [[word substringToIndex:1] uppercaseString];
NSMutableArray *letterList = [dict objectForKey:firstLetter];
if (!letterList) {
letterList = [NSMutableArray array];
[dict setObject:letterList forKey:firstLetter];
}
[letterList addObject:word];
}
NSLog(#"%#", dict);

Answer 2

You can achieve what you want through the following steps:
Create an empty but mutable dictionary.
Get the first character.
If a key for that character does not exist, create it.
Add the word to the value of the key (should be an NSMutableArray).
Repeat step #2 for all keys.
Here is the Objective-C code for these steps. Note that I am assuming that you want the keys to be case insensitive.
// create our dummy dataset
NSArray * wordArray = [NSArray arrayWithObjects:#"Apple",
#"Pickle", #"Monkey", #"Taco",
#"arsenal", #"punch", #"twitch",
#"mushy", nil];
// setup a dictionary
NSMutableDictionary * wordDictionary = [[NSMutableDictionary alloc] init];
for (NSString * word in wordArray) {
// remove uppercaseString if you wish to keys case sensitive.
NSString * letter = [[word substringWithRange:NSMakeRange(0, 1)] uppercaseString];
NSMutableArray * array = [wordDictionary objectForKey:letter];
if (!array) {
// the key doesn't exist, so we will create it.
[wordDictionary setObject:(array = [NSMutableArray array]) forKey:letter];
}
[array addObject:word];
}
NSLog(#"Word dictionary: %#", wordDictionary);

Answer 3

Take a look at this topic, they solves almost the same problem as you — filtering NSArray into a new NSArray in objective-c Let me know if it does not help so I will write for you one more code sample.

Answer 4

Use this to sort the contents of array in alphabetical order, further you design to the requirement
[keywordListArr sortUsingSelector:#selector(localizedCaseInsensitiveCompare:)];

Answer 5

I just wrote this sample. It looks simple and does what you need.
NSArray *names = [NSArray arrayWithObjects:#"Anna", #"Antony", #"Jack", #"John", #"Nikita", #"Mark", #"Matthew", nil];
NSString *alphabet = #"ABCDEFGHIJKLMNOPQRSTUWXYZ";
NSMutableDictionary *sortedNames = [NSMutableDictionary dictionary];
for(int characterIndex = 0; characterIndex < 25; characterIndex++) {
NSString *alphabetCharacter = [alphabet substringWithRange:NSMakeRange(characterIndex, 1)];
NSArray *filteredNames = [names filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"SELF BEGINSWITH[C] %#", alphabetCharacter]];
[sortedNames setObject:filteredNames forKey:alphabetCharacter];
}
//Just for testing purposes let's take a look into our sorted data
for(NSString *key in sortedNames) {
for(NSString *value in [sortedNames valueForKey:key]) {
NSLog(#"%#:%#", key, value);
}
}