Create array of dictionaries in objective c - objective-c

Question

I am fetching dictionaries from my local database.
My database array with name aryTitle_DB structure is as mentioned below.
( {
"date":13/9/2014;
"title"="abc"
}, { "date":13/9/2014;
"title"="def" }, { "date":13/9/2014;
"title"="ghi" }, {"date":14/9/2014;
"title"="abc" }, { "date":15/9/2014;
"title"="abc" }, { "date":15/9/2014;
"title"="def" })
I need following type of array structure from aryTitle_DB
( { "13/9/2014":("abc","def","ghi") }, { "14/9/2014":("abc") }, { "15/9/2014":("abc","def") } )
I did lot of search in stack overflow and in other tutorials but unable to find it.
please help to create such kind of array structure.
Help will be appreciable.

Answer 1

NSMutableArray *fromDB;
NSMutableArray *filtered;
filtered = [NSMutableArray new];
while (fromDB.count > 0){
NSDictionary *uniqueDate;
NSArray *filteredDate;
NSMutableArray *newDate;
uniqueDate = fromDB[0];
filteredDate = [fromDB filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"self.date=%K",uniqueDate[#"date"]]];
[fromDB removeObjectsInArray:filteredDate];
newDate = [NSMutableArray new];
for (NSDictionary *oneDate in filteredDate) {
[newDate addObject:oneDate[#"title"]];
}
uniqueDate = #{uniqueDate[#"date"]:newDate};
[filtered addObject:uniqueDate];
};
this code should work. may be format of predicate should be changed, because i didn't test it. instead of format you can use formated string with filled var field.

Answer 2

In objective-C, there is no generics, this has only arrived with Swing in fact.
So your data structure is only a classical a NSArray of NSDictionary.
If you want to declare this ( { "13/9/2014":("abc","def","ghi") }, { "14/9/2014":("abc") }, { "15/9/2014":("abc","def") } ) in objC you ay do it like that
NSMutableArray* result = [NSMutableArray new];
NSDictionary * dict = [NSDictionary new];
// With Modern objective C syntax, it would be like that :
dict["13/9/2014"] = #{"abc","def","ghi"};
dict["14/9/2014"] = #{"abc"};
dict["15/9/2014"] = #{"abc","def"};
[result addObject:dict];
But of course you can create intermediate NSMutableArray for each values and use setValue:ForKey: method of NSDictionary to add it to dictionary.
Edit : added algorithm to parse DB answer
NSArray*DBAnswer; // this is your array containing the answer from the DB
NSDictionary*result=[NSDictionary new];
for(NSDictionary*d in DBAnswer)
{
NSMutableArray*list;
if(![result containsKey:d["date"]])
{
list = [NSMutableArray new];
result[d["date"]] = list;
}
else
{
list = result[d["date"]];
}
[list addObject:d["title"]];
}
// After that you have the structure in the result NSDictionary