NSPredicates : A handy tool

Hi all,

Searching and sorting is an utmost important part of any iOS app, i believe so...

Lets try to use a simpler way provided by Apple named NSPredicates that make development easier..

:) :)

We have numerous situations where NSPredicates play an important role, very few are here..

Ohhh...list may increase

:)

1) Filter an array of objects

Basic

•     I have an array : arrCustomObjects 
•     It contains objects of type : CustomObject
•     Properties of CustomObject : iD, name
•     Data :
• [@"32"   , @"Maria"] 
• [@"51"   , @"John"] 
• [@"100" , @"Stuart"] 
• [@"500" , @"Barbie"]

What to do

•  Search object from arrCustomObjects where id = @"32" 

How To do

  

 NSPredicate *predicate = [NSPredicate predicateWithFormat:@"iD == %@", @"32"];

 NSMutableArray *filtered = (NSMutableArray*)[arrCustomObjects 

                                       filteredArrayUsingPredicate:predicate];

  if(filtered.count>0)

     CustomObject *customObject  = [filtered objectAtIndex:0];

====================================================================

2) Filter in form of Sets

What to do

• Filter array that contains only my favorite female friends

How To do

 NSArray *girlsArray = [NSArray arrayWithObjects:@"Barbie",@"Maria"];

 NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name IN %@", girlsArray];

 NSMutableArray *filtered = (NSMutableArray*)[arrCustomObjects 

                                       filteredArrayUsingPredicate:predicate];

  if(filtered.count>0)

    CustomObject *customObject  = [filtered objectAtIndex:0];

====================================================================

3) Filter using Regular Expressions

What To do

• Email ID validation using regex

How To do

 NSString *emailRegex =

    @"^(?i)(?:(?:https?|ftp):\\/\\/)?(?:\\S+(?::\\S*)?@)?(?:(?:[1-9]\\d?|1\\d\\d|2[01]\\d|22[0-3])(?:\\.(?:1?\\d{1,2}|2[0-4]\\d|25[0-5])){2}(?:\\.(?:[1-9]\\d?|1\\d\\d|2[0-4]\\d|25[0-4]))|(?:(?:[a-z\\u00a1-\\uffff0-9]+-?)*[a-z\\u00a1-\\uffff0-9]+)(?:\\.(?:[a-z\\u00a1-\\uffff0-9]+-?)*[a-z\\u00a1-\\uffff0-9]+)*(?:\\.(?:[a-z\\u00a1-\\uffff]{2,})))(?::\\d{2,5})?(?:\\/[^\\s]*)?$";

    NSPredicate *regextest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",  emailRegex];

    

    if ([regextest evaluateWithObject: url] == YES) 

        NSLog(@"URL is valid!");

    else 

        NSLog(@"URL is not valid!");

Enjoy the ease :) :)