Sort an array of objects by an objects value - ios

Question

I have an array of objects that I parse from a JSON. My JSON looks like this;
- message: [
-{
movie_id: 30,
movie_name: "Scream",
category_name: "Horror"
},
-{
movie_id: 31,
movie_name: "Avengers",
category_name: "Action"
},
-{
movie_id: 32,
movie_name: "Friday the 13th",
category_name: "Horror"
},
-{
movie_id: 33,
movie_name: "The ring",
category_name: "Horror"
},
-{
movie_id: 34,
movie_name: "Die Hard",
category_name: "Action"
},
-{
movie_id: 35,
movie_name: "The ring 2",
category_name: "Horror"
},
....
Its a JSON array of movies that contains many movies. What I am unable to do is parse each object and arrange them by category_name in an array, so all the "horror" will be grouped together, all the action, and all the romance etc etc. However...I need to be able to place a String value at the start of each category. So the array might look like this:
Index
0 "Horror"
1 Movie Object
2 Movie Object
3 Movie Object
4 "Romance"
5 Movie Object
6 Movie Object
7 "Action"
8 Movie Object
9 Movie Object
10 Movie Object
I have movie object with the following paramters;
NSString *movie_id
NSString * movie_name
NSString *category_name
Any help is greatly appreciated.

Answer 1

I would suggest a slightly different structure for the parsed data.
Rather than an array of mixed strings and objects, why not create a dictionary (using the category names as keys) of arrays? Just iterate through your original JSON. For each movie object, check to see if the key exists for that category name. If it does not, add a new array as the value for that category name. Then add the movie object to the array.
Your final dictionary would be something like this:
#{ #"Horror" : #[obj1, obj2, obj 3],
#"Romance" : #[obj4, obj5, obj 6],
#"Action" : #[obj7, obj8, obj 9] }
That way you can iterate through each category, and also iterate through the movies is each category

Answer 2

Suppose You have your array message then you can arrange them as
NSArray *categories = [message valueForKeyPath:#"#distinctUnionOfObjects.category_name"];
NSMutableArray *results = [NSMutableArray new];
for (NSString *categoryName in categories)
{
NSArray *groupArray = [message filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"category_name = %#", categoryName]];
[results addObject:categoryName];
[results addObjectsFromArray:groupArray];
}
and your final array I mean results will be
(
Horror,
{
"category_name" = Horror;
"movie_id" = 30;
"movie_name" = Scream;
},
{
" movie_name" = "Friday the 13th";
"category_name" = Horror;
"movie_id" = 32;
},
{
"category_name" = Horror;
"movie_id" = 33;
"movie_name" = "The ring";
},
{
"category_name" = Horror;
"movie_id" = 35;
"movie_name" = "The ring 2";
},
Action,
{
"category_name" = Action;
"movie_id" = 31;
"movie_name" = Avengers;
},
{
"category_name" = Action;
"movie_id" = 34;
"movie_name" = "Die Hard";
}
)
Hope this is what you want.
But this not a good coding practice, to have different data types(string and dictionary) in same array. so you should parse them like this
NSArray *categories = [message valueForKeyPath:#"#distinctUnionOfObjects.category_name"];
NSMutableDictionary *results = [NSMutableDictionary new];
for (NSString *categoryName in categories)
{
NSArray *groupArray = [message filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"category_name = %#", categoryName]];
[results setObject:groupArray forKey:categoryName];
}
and your result will be.
{
Action = (
{
"category_name" = Action;
"movie_id" = 31;
"movie_name" = Avengers;
},
{
"category_name" = Action;
"movie_id" = 34;
"movie_name" = "Die Hard";
}
);
Horror = (
{
"category_name" = Horror;
"movie_id" = 30;
"movie_name" = Scream;
},
{
" movie_name" = "Friday the 13th";
"category_name" = Horror;
"movie_id" = 32;
},
{
"category_name" = Horror;
"movie_id" = 33;
"movie_name" = "The ring";
},
{
"category_name" = Horror;
"movie_id" = 35;
"movie_name" = "The ring 2";
}
);
}
Now choose whatever you want.