Parse JSON to a tree structure - ios

Question

I'm working on a project that requires a tableView list of categorized grocery items. Each category can have n depth. The JSON response from the API looks like this.
"items":[
{
"id":"5366f8d3e4b0e44dc2d4a6fb",
"name":"String Cheese"
"description":"Sargento String Cheese",
"categorization":[
[
"Dairy",
"Cheese"
]
]
},
{
"id":"5366f8d3e4b0e44dc2d1a6fb",
"name":"Budlight 6-pk"
"description":"Budlight 12-pk",
"categorization":[
[
"Beverages",
"Alcohol",
"Beer"
]
]
}
]
Right now I'm creating Item objects from the item dictionaries and storing them in a mutable array like below.
NSArray *itemsArray = [response objectForKey:items];
NSMutableArray *itemsMutableArray = [[NSMutableArray alloc] init];
for(NSDictionary *itemDict in itemsArray){
Item *itemObj = [[Item alloc] initWithDictionary:itemDict]
[itemsMutableArray addObject:itemObj];
}
I would like to loop through itemsMutableArray and create a tree data structure that has a path from the root to each of the items. Then, I would like to be able to use the tree as a datasource for tableViews in each level of category.
Here's what my Item class header looks like.
#interface Item : NSObject
#property (nonatomic, strong) NSString *id;
#property (nonatomic, strong) NSString *name;
#property (nonatomic, strong) NSString *description;
#property (nonatomic, strong) NSArray *categorization;
#end
...and the implementation
#import "Item.h"
#implementation Item
- (id)initWithDictionary:(NSDictionary *)objDictionary{
if (self = [super init]) {
self.id = [objDictionary valueForKey:#"id"];
self.name = [objDictionary valueForKey:#"name"];
self.description = [objDictionary valueForKey:#"description"];
self.categorization = [objDictionary valueForKey:#"categorization"];
}
return self;
}
#end
I am not very familiar with tree data structures and recursion. I would greatly appreciate any help on how to approach this. Thanks!

Answer 1

If you need simple node tree data structure. How about this way?
Hope this little help.
Header
#interface ItemCategory : NSObject
#property (nonatomic, strong) NSString *name;
#property (nonatomic) ItemCategory *parent;
#property (nonatomic, strong) NSMutableArray *children;
-(id)initWithName:(NSString *)n parent:(ItemCategory *)p;
#end
#interface CategoryTree : NSObject
#property (nonatomic, strong) ItemCategory *root;
-(ItemCategory *)_getChildCategory:(ItemCategory *)category name:(NSString *)name;
-(ItemCategory *)_addChildCategory:(ItemCategory *)category name:(NSString *)name;
-(void)_dumpCategory:(ItemCategory *)category depth:(int)depth;
-(void)dump;
-(ItemCategory *)getCategory:(NSArray *)arr;
-(void)addCategory:(NSArray *)arr;
#end
Source
#implementation CategoryTree
#synthesize root;
-(id)init {
if (self = [super init]) {
root = [[ItemCategory alloc] initWithName:#"root" parent:nil];
}
return self;
}
-(ItemCategory *)_getChildCategory:(ItemCategory *)category name:(NSString *)name {
for (ItemCategory *child in category.children)
if ([child.name isEqualToString:name])
return child;
return nil;
}
-(ItemCategory *)_addChildCategory:(ItemCategory *)category name:(NSString *)name {
ItemCategory *child = [self _getChildCategory:category name:name];
if (child)
return child;
child = [[ItemCategory alloc] initWithName:name parent:category];
[category.children addObject:child];
return child;
}
-(void)_dumpCategory:(ItemCategory *)category depth:(int)depth{
NSString *parentStr = #"";
ItemCategory *parent = category.parent;
while (parent) {
parentStr = [NSString stringWithFormat:#"%#%#%#", parent.name, parentStr.length > 0 ? #">" : #"", parentStr];
parent = parent.parent;
}
NSLog(#"%#%#%#", parentStr, parentStr.length > 0 ? #">" : #"", category.name);
for (ItemCategory *child in category.children) {
[self _dumpCategory:child depth:depth + 1];
}
}
-(void)dump {
[self _dumpCategory:root depth:0];
}
-(ItemCategory *)getCategory:(NSArray *)arr {
ItemCategory *category = root;
for (NSString *categoryName in arr) {
category = [self _getChildCategory:category name:categoryName];
if (!category)
return nil;
}
return category;
}
-(void)addCategory:(NSArray *)arr {
if ([self getCategory:arr])
return;
ItemCategory *category = root;
for (NSString *categoryName in arr) {
ItemCategory *childCategory = [self _getChildCategory:category name:categoryName];
if (!childCategory) {
childCategory = [self _addChildCategory:category name:categoryName];
}
category = childCategory;
}
}
#end
Usage
CategoryTree *tree = [[CategoryTree alloc] init];
[tree addCategory:#[#"Dairy", #"Cheese"]];
[tree addCategory:#[#"Dairy", #"Milk"]];
[tree addCategory:#[#"Beverages", #"Alcohol", #"Beer"]];
[tree addCategory:#[#"Beverages", #"Alcohol", #"Wine"]];
[tree addCategory:#[#"Beverages", #"Non-Alcohol", #"Cola"]];
[tree dump];
Result
root
root>Dairy
root>Dairy>Cheese
root>Dairy>Milk
root>Beverages
root>Beverages>Alcohol
root>Beverages>Alcohol>Beer
root>Beverages>Alcohol>Wine
root>Beverages>Non-Alcohol
root>Beverages>Non-Alcohol>Cola

Answer 2

well I have found a way to implement what you need. I do not know how optimised it is since i do not how many items you'll be receiving . The implementation is given below.
You need to start with adding this dictionary in Item.h #property (nonatomic, strong) NSMutableDictionary *catTree;
Next do this to get the tree
[itemsMutableArray enumerateObjectsUsingBlock:^(Item *itm, NSUInteger i,BOOL *stop){
itm.catTree = [NSMutableDictionary dictionary];
NSString *dairy = #"",*beverage = #"";
for (NSArray *catArray in itm.categorization) {
/*
Everything below is written assuming the format of the JSON will be "as-is"
*/
if ([catArray containsObject:#"Dairy"]) {
//Take everything except Dairy
NSArray *stripedArray = [catArray filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"SELF != \"Dairy\""]];
int i = 0;
//Loop through the array to get any sub categories.
while (i < stripedArray.count) {
dairy = [dairy stringByAppendingString:[NSString stringWithFormat:(i == stripedArray.count-1)?#"%# ":#"%#->",stripedArray[i]]]; //Space at the end to account for similar entry in the same category for e.g two dairy products.
i++;
}
} else if ([catArray containsObject:#"Beverages"]) {
NSArray *stripedArray = [catArray filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"SELF != \"Beverages\""]];
int i = 0;
while (i < stripedArray.count) {
beverage = [beverage stringByAppendingString:[NSString stringWithFormat:(i == stripedArray.count-1)?#"%# ":#"%#->",stripedArray[i]]];
i++;
}
}
}
//Set the category tree for every item using a dictionary
[itm.catTree setValue:dairy forKey:#"Dairy"];
[itm.catTree setValue:beverage forKey:#"Beverage"];
NSLog(#"%#",itm.catTree);
}];
the above code gives the following output for your json
{
Beverage = "";
Dairy = "Cheese ";
}
{
Beverage = "Alcohol->Beer ";
Dairy = "";
}
For multiple beverages
{
Beverage = "Alcohol->Beer Alcohol->Wine->Red Soda->Coke ";
Dairy = "";
}
Hope this helps.