Category Archives: iOS

Searching an NSArray of NSDictionaries

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NSPredicate is the simplest way to do it.

Given Data like this:

NSArray *theArray = @[@{@"id":1,"name":@"one"},@{@"id":2,"name":@"two"},@{@"id":3,"name":@"three"}];
NSPredicate *p = [NSPredicate predicateWithFormat:@"id = 291"]; //fiber
NSArray *matchedDicts = [theArray filteredArrayUsingPredicate:p];

There is much more to NSPredicate. I used exact matching, but matching with BEGINSWITH, CONTAINS, ENDSWITH, and LIKE. In some examples you’ll also see [c] or [cd] next to these keywords. The ‘c’ means it searches case insensitively and the ‘d’ means that an ‘o’ with an umlaut is still just an ‘o’.

Getting the Day of the Week from an NSDate

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I am trying to get a custom day of the week format like this: Su, M, T, W, Th, F, S.

I’d really like to be able to compare numbers and get 0-6 instead of the full name(Wednesday) or the 3 letter day (Wed). I found this great resource for the NSDateFormatter codes. It turns out that ‘E’ is the 3 letter name and just ‘e’ is the number! The problem I found was that ‘e’ was not zero based, so I had to put a pad into my NSArray that gives my custom weekday string.

	NSDate *now = [NSDate date];
	NSDateFormatter *nowDateFormatter = [[NSDateFormatter alloc] init];
	NSArray *daysOfWeek = @[@"",@"Su",@"M",@"T",@"W",@"Th",@"F",@"S"];
	[nowDateFormatter setDateFormat:@"e"];
	NSInteger weekdayNumber = (NSInteger)[[nowDateFormatter stringFromDate:newDate] integerValue];
	NSLog(@"Day of Week: %@",[daysOfWeek objectAtIndex:weekdayNumber]);

Output (It’s Wednesday):
Day of Week: W

Walking through the code I created a date named ‘now’. Then I created an NSDateFormatter followed by an NSArray of the custom daysOfWeek. I’m using Objective-C literals so I don’t need to end in ‘nil’. I also added a string for the zero element as this output is not zero based so it will never be zero, but it will go from 1-7 for Sunday-Saturday. I then use the format string of @”e” to get just that number and in the next line I create an NSInteger and it’s not a pointer because NSIntegers is basically just a C int. The NSDateFormatter will return a string no matter what and since I know I’m getting a number I just use the NSString ‘integerValue’ to cast and it returns an NSUInteger. NSUInteger is an ‘unsigned int’ variable and NSInteger is just an ‘int’. I could have used either but these numbers will always be small so an NSInteger works just fine.

Programmatically Setting a UISegmentedControl From IB

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I added my UISegmentedControl from Interface Builder easily enough. I just wanted needed to change it to the needs of the data.

BUT…since I added it in interface builder I cannot use initWithArray: so I need to connect it up in Xcode, clear it out and then add in what I need. Then we’ll update the app when the UISegmentedControl is updated.

@interface TopicViewController : UIViewController
 
@property (strong, nonatomic) IBOutlet UIButton *filterButton;
@property (strong, nonatomic) IBOutlet UISegmentedControl *filterSegmented;
 
-(void)segmentChanged:(id)sender;

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