Sequentially ordered NSMutableArray - replacing breaks in order - ios

Question

I've been having a mind blank over this problem, so I thought maybe some of you could shed a light on the situation.
To cut a long story short, I am building an app that fetches a school student's timetable from a server, parses it, and displays it in a table view. Each student has 7 periods per day, and there are 10 days in the timetable spanning across a fortnight (5 days in Week A, 5 days in Week B).
However the problem lies where some students have free periods - that is, they do not have a class during that period. Because the server does not take free periods into account, some students might return 70 total periods in the fortnight, whereas another might return 66.
Cutting to the chase here...
I have an ordered NSMutableArray full of NSDictionaries. A typical object in the array would look like this when outputted to the console:
{
weekday = 12;
period = 1;
room = "Room D404";
title = "English Extension";
},
I need to figure out where there is a break in the order, and if so, insert an object into it to fill the blank. Let me give you an example:
{
dayweek = 12;
period = 1;
room = "Room D404";
title = "English Extension";
},
{
dayweek = 12;
period = 2;
room = "Room W285";
title = "Modern History";
},
{
dayweek = 12;
period = 3;
room = "Room W187";
title = "Maths Extension 1";
},
{
dayweek = 12;
period = 4;
room = "Room W370";
title = Economics;
},
{
dayweek = 12;
period = 6;
room = "Room D301";
title = "English Advanced";
},
{
dayweek = 12;
period = 7;
room = "Room W282";
title = "Studies of Religion";
},
{
dayweek = 13;
period = 1;
room = "Room W370";
title = Economics;
},
There is no object where period = 5, so I need to add one. Is what I'm saying hard to understand? Sorry if it is.
Thanks in advance!

Answer 1

This fills in missing periods from 1 to the last existing on a day. It does not fill days to a given minimum of periods.
NSMutableArray periods; // from somewhere else
NSUInteger count = [periods count];
NSUInteger currentPeriod = 0;
NSUInteger currentDayweek = 0;
for (NSUInteger i = 0; i < count; ++i)
{
NSDictionary *periodDescription = periods[i];
NSUInteger dayweek = [periodDescription[#"dayweek"] unsignedIntegerValue];
if (dayweek != currentDayweek) {
// another day
currentPeriod = 0;
currentDayweek = dayweek;
}
NSUInteger period = [periodDescription[#"period"] unsignedIntegerValue];
currentPeriod += 1;
while (period > currentPeriod) {
NSDictionary *fillIn = #{ #"dayweek" : #(dayweek), #"period" : #(currentPeriod), #"room" : #"cafeteria", #"title" = "taking a break" };
[periods insertObject:fillIn atIndex:i];
currentPeriod += 1;
i += 1;
count += 1;
}
}
If you do not want to fill morning hours before the first existing period, add this directly before the while loop:
if (currentPeriod == 1)
currentPeriod = period;
Note: Typed in browser, errors are probable.

Answer 2

Try this and let me know if you are getting any issues
for (int i = 1; i<=self.arrayForRows.count; i++)
{
if ([[[self.arrayForRows objectAtIndex:i]valueForKey:#"period"] intValue] == i)
{
}
else
{
// Insert Here as [self.arrayForRows insertObject:yourObject atIndex:i];
i=i-1;
}
}

Answer 3

This is only a partial answer, but too long to post as a comment.
The purpose of this snippet is only to identify missing periods with a minimal amount of code. You would need to do it in a loop for all days of the fortnight, of course.
To do this you can use predicates:
// For each day create a list of all periods.
// This is just a hard coded example
NSArray *allPeriodsForDay = #[#(1),#(2),#(3),#(4),#(5),#(6)];
// Get an array of the periods actually in the list
// It will look like this: #[#(1),#(2),#(4),#(5),#(6)]; // Period 3 missing
NSArray *studentsPeriods = [periodRecords valueForKey: #"period"];
// Build a predicate to identify period(s) not in list
NSPredicate *freePredicate = [NSPredicate predicateWithFormat:#"not self in %#", studentsPeriods];
NSArray *freePeriods = [allPeriodsForDay filteredArrayUsingPredicate:freePredicate];
freePeriods now contains a list of the "missing" periods in the students' schedule for that day.
You can then create a new NSDictionary and add it to the list. Then sort it all by the period field.