Using NSPredicate to filter an NSArray based on NSDictionary keys

Question

I have an array of dictionaries   I want to filter the array based on a key   I tried this   NSPredicate  predicate    NSPredicate predicateWithFormat    SPORT             Football     NSArray  filteredArray    data filteredArrayUsingPredicate predicate     This doesn t work  I get no results  I think I m doing something wrong  I know this is the method if  SPORT  was an ivar  I think it is probably different if it is a key   I haven t been able to find an example however   Thanks    Update  I added quotes around the string I am searching for   NSPredicate  predicate    NSPredicate predicateWithFormat    SPORT               Football      It still does not work     Update 2  Solved it  I actually had to remove the single quotes  which seems to go against what the guide says   My real problem is I had a nested array and I wasn t actually evaluating the dictionaries  Bone head move

User · Answer

I know it s old news but to add my two cents  By default I use the commands LIKE cd  rather than just  c   The  d  compares letters with accent symbols  This works especially well in my Warcraft App where people spell their name  V    d      making it nearly impossible to search for their name in a tableview  The  d  strips their accent symbols during the predicate  So a predicate of   name LIKE CD       object name where object name      voodoo  will return the object containing the name V    d       From the Apple documentation  like cd  means    case- and diacritic-insensitive like      For a complete description of the string syntax and a list of all the operators available  see Predicate Format String Syntax

User · Answer

Looking at the NSPredicate reference  it looks like you need to surround your substitution character with quotes  For example  your current predicate reads   SPORT    Football  You want it to read  SPORT     Football    so your format string needs to be    SPORT

User · Answer

NSPredicate is only available in iPhone 3 0    You won t notice that until try to run on device

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With Swift 3  when you want to filter an array of dictionaries with a predicate based on dictionary keys and values  you may choose one of the following patterns      1  Using NSPredicate init format arguments   initializer  If you come from Objective-C  init format arguments   offers a key-value coding style to evaluate your predicate   Usage   import Foundation  let array      key1    value1    key2    value2      key1    value3      key3    value4     let predicate   NSPredicate format   key1          value1     let predicate   NSPredicate format   self  key1            value1      also works let filteredArray   array filter predicate evaluate   print filteredArray     prints     key2    value2    key1    value1         2  Using NSPredicate init block   initializer  As an alternative if you prefer strongly typed APIs over stringly typed APIs  you can use init block   initializer   Usage   import Foundation  let array      key1    value1    key2    value2      key1    value3      key3    value4     let dictPredicate   NSPredicate block     obj     in     guard let dict   obj as   String  String   let value   dict  key1   else   return false       return value     value1      let filteredArray   array filter dictPredicate evaluate  print filteredArray     prints     key2    value2    key1    value1

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import  lt Foundation Foundation h gt     clang -framework Foundation Siegfried m      int main         NSArray  arr                  1      Fafner                1      Fasolt              NSPredicate  p    NSPredicate predicateWithFormat            SELF  1   CONTAINS  e         NSArray  res    arr filteredArrayUsingPredicate p       NSLog   Siegfried      res       return 0

User · Answer

It should work - as long as the data variable is actually an array containing a dictionary with the key SPORT  NSArray  data    NSArray arrayWithObject  NSMutableDictionary dictionaryWithObject   foo  forKey   BAR         NSArray  filtered    data filteredArrayUsingPredicate  NSPredicate predicateWithFormat    BAR            foo       Filtered in this case contains the dictionary     the    does not have to be quoted  this is done when NSPredicate creates the object

[objective-c] Using NSPredicate to filter an NSArray based on NSDictionary keys

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