Getting NSmutableDictionary key from two mutable arrays - ios

Question

I have three mutable arrays
#interface PickeriviewAndTableViewController ()
//Create mutableArray for tableView
#property(strong,nonatomic)NSMutableArray *msgYear;
#property(strong,nonatomic)NSMutableArray *msgSeason;
#property(strong,nonatomic)NSMutableArray *msgCourse;
I want to add element to array msgCourse[ ] using the key generating from the first two arrays msgYear[ ] and msgSeason[ ].
Then I want to populate the msgCourse[] array using a button
- (IBAction)addCourse:(UIButton *)sender {
//To get value from pickerView, prepare for key and contents
NSInteger numRow=[picker selectedRowInComponent:kNumComponent];//0=1st,1=2nd,etc
NSInteger SeaRow=[picker selectedRowInComponent:kSeaComponent];//0=fall,1=spring,2=summer
NSInteger CourseRow=[picker selectedRowInComponent:kCourseComponent];
NSString *num=Number[numRow];
NSString *season=Season[SeaRow];
NSString *course=Course[CourseRow];
NSString *CourseToAdd=[[NSString alloc ]initWithFormat:#"%# ",course];
NSString *SeasonToAdd=[[NSString alloc ]initWithFormat:#"%# ",season];
NSString *YearToAdd=[[NSString alloc ]initWithFormat:#"%# ",num];
// Try to generate key from YearToAdd and SeasonToAdd and fill in content
NSMutableArray *keys = [[NSMutableArray alloc] init];
NSMutableDictionary *contents = [[NSMutableDictionary alloc] init];
NSString *keyFromYearAndSeason = #"Don't_know_what_to_do_here";
[contents setObject:[NSArray arrayWithObjects:#"Don't_know_how", nil] forKey:keyFromYearAndSeason];
[keys addObject:keyFromYearAndSeason];
[self setSectionKeys:keys];
[self setSectionContents:contents];
}
My question is: How to complete my code by replacing these "Don't know how" lines of code here please?
Update: To be more clear, key is generating from msgYear[ ] and msgSeason[ ] e.g. '2001 fall', dictionary is filled with course e.g. 'chemistry','math'.

Answer 1

The link to your other question helped provide context for what you are trying to achieve.
You don't need to create a dictionary or an array inside the addButtton method - you should have your dictionary as a property that is already initialised.
Then, in add button you retrieve the array associated with the key - if the value is nil then you create a new array and put the course in. If the value isn't nil simply add the course to the array.
#property (strong,nonatomic) NSMutableDictionary *tableEntries; // alloc/init this in viewDidLoad
- (IBAction)addCourse:(UIButton *)sender {
//To get value from pickerView, prepare for key and contents
NSInteger numRow=[picker selectedRowInComponent:kNumComponent];//0=1st,1=2nd,etc
NSInteger SeaRow=[picker selectedRowInComponent:kSeaComponent];//0=fall,1=spring,2=summer
NSInteger CourseRow=[picker selectedRowInComponent:kCourseComponent];
NSString *num=Number[numRow];
NSString *season=Season[SeaRow];
NSString *course=Course[CourseRow];
NSString *key=[NSString stringWithFormat:#"%# %#",num,season];
NSMutableArray *courses=self.tableEntries[key];
if (courses == nil) {
courses=[NSMutableArray new];
self.tableEntries[key]=courses;
}
[courses addObject:course];
}
NSDictionarys are unordered, so you need to give some thought to how you want to order the data in your table. You could use an array to hold the keys as in your original code and then sort this array.