remove duplicates from object array [duplicate] - objective-c

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This question already has answers here:
Removing duplicates from array based on a property in Objective-C
(8 answers)
Closed 7 years ago.
ok new to objective c.
I have my app going to a web site and pulling company data. Company name address etc. I want to display the state from each company. But I only want one of each state shown. For example if I have CA,CA,CA,AZ,AZ,AZ,NY. I only want to display on my tableview CA,AZ,NY. I am have tried distinctUnionOfObjects, but I think I am using it wrong. any help?
#import "StatesTableViewController.h"
#interface StatesTableViewController ()
#end
#implementation StatesTableViewController
NSArray *companies;
- (void)viewDidLoad {
[super viewDidLoad];
NSString *address = #"http://www.Feed";
NSURL *url = [[NSURL alloc] initWithString:address];
//laod the data on a background queue..
//if we were connecting to a an online url then we need it
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
companies = [self readCompanies:url];
//now that we have the data, reload the table data on the main ui thread
[self.tableView performSelectorOnMainThread:#selector(reloadData) withObject:nil waitUntilDone:YES];
});
}
//new code
- (NSArray *)readCompanies:(NSURL *)url {
//create a nsurlrequest with the given Url
NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:
NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:30.0];
//get the data
NSURLResponse *response;
NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];
//now create a nsdictionary from the json data
NSDictionary *jsonDictionary = [NSJSONSerialization JSONObjectWithData:data
options:0 error:nil];
//create a new array to hold the comanies
NSMutableArray *companies = [[NSMutableArray alloc] init];
//get an array of dictionaries with the key "company"
NSArray *array = [jsonDictionary objectForKey:#"companies"];
//iterate throught the array of dictionaries
for (NSDictionary *dict in array) {
//create a new company object with information in the dictionary
Company *company = [[Company alloc] initWithJSONDictionary:dict];
//add the Company object to the array
[companies addObject:company];
}
//return the array of Company objects
return companies;
}
//trying to get 1 state here? should i create a new array?
//added code to show 1 of each state. companies array now uniquevalues
//NSArray* uniqueValues = [companies valueForKeyPath:[NSString stringWithFormat:#"distinctUnionOfObjects.%#",#"state"]];
//or
//static NSArray *uniqueValues = nil;
//if (uniqueValues == nil){
// uniqueValues = [NSArray arrayWithArray:[companies valueForKeyPath:[NSString stringWithFormat:#"distinctUnionOfObjects.%#",#"state"]]];
//}
//or
//companies = [companies valueForKeyPath:#"#distinctUnionOfObjects.state"];
//end added code
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#pragma mark -table view controller methods
//change uniqueValue errors to companies
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger) section {
// return [uniqueValues count];
return [companies count];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *cellID = #"CellIDState";
UITableViewCell *cell = [self.tableView dequeueReusableCellWithIdentifier:cellID];
if (cell == nil){
//single line on table view
//cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:cellID];
// dual line on table view
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:cellID];
}
//Company *company = [uniqueValues objectAtIndex:indexPath.row];
Company *company = [companies objectAtIndex:indexPath.row];
//cell.textLabel.text = company.company_id;
cell.textLabel.text = company.state;
cell.detailTextLabel.text = [NSString stringWithFormat:#"%#",company.companyName];
//adds cheveron to tableviewl
[cell setAccessoryType: UITableViewCellAccessoryDisclosureIndicator];
return cell;
}
#pragma mark - navigation
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
}
#end

Answer 1

Suppose you have a Company object with the following interface:
#interface Company : NSObject
#property (nonatomic) NSString *name;
#property (nonatomic) NSString *state;
#end
Next, let's say you do the following:
// Creating & adding a few companies
Company *company1 = [Company new];
company1.name = #"Some Company";
company1.state = #"CA";
Company *company2 = [Company new];
company2.name = #"Some Company";
company2.state = #"CA";
Company *company3 = [Company new];
company3.name = #"Some Company";
company3.state = #"CA";
Company *company4 = [Company new];
company4.name = #"Some Company";
company4.state = #"AZ";
Company *company5 = [Company new];
company5.name = #"Some Company";
company5.state = #"AZ";
self.companies = #[company1, company2, company3, company4, company5];
NSArray *uniqueStates = [self.companies valueForKeyPath:#"#distinctUnionOfObjects.state"];
NSSet *uniqueStatesSet = [NSSet setWithArray:[self.companies valueForKey:#"state"]];
The uniqueStates array & uniqueStatesSet set will both contain two objects, #"CA" and #"AZ" (two ways of getting a unique set objects).

Answer 2

NSArray *companies = …;
NSOrderedSet *states = [NSOrderedSet orderedSetWithArray:[companies valueForKey:#"state"]];
If you have an ordered list of unique items, you should use an ordered set to model it.