Case insensitive comparison NSString

Can anyone point me to any resources about case insensitive comparison in Objective C? It doesn't seem to have an equivalent method to str1.equalsIgnoreCase(str2)

if( [@"Some String" caseInsensitiveCompare:@"some string"] == NSOrderedSame ) {
  // strings are equal except for possibly case
}

The documentation is located at Search and Comparison Methods

 NSString *stringA;
 NSString *stringB;

 if (stringA && [stringA caseInsensitiveCompare:stringB] == NSOrderedSame) {
     // match
 }

Note: stringA && is required because when stringA is nil:

 stringA = nil;
 [stringA caseInsensitiveCompare:stringB] // return 0

and so happens NSOrderedSame is also defined as 0.

The following example is a typical pitfall:

 NSString *rank = [[NSUserDefaults standardUserDefaults] stringForKey:@"Rank"];
 if ([rank caseInsensitiveCompare:@"MANAGER"] == NSOrderedSame) {
     // what happens if "Rank" is not found in standardUserDefaults
 }

An alternative if you want more control than just case insensitivity is:

[someString compare:otherString options:NSCaseInsensitiveSearch];

Numeric search and diacritical insensitivity are two handy options.

You could always ensure they're in the same case before the comparison:

if ([[stringX uppercaseString] isEqualToString:[stringY uppercaseString]]) {
    // They're equal
}

The main benefit being you avoid the potential issue described by matm regarding comparing nil strings. You could either check the string isn't nil before doing one of the compare:options: methods, or you could be lazy (like me) and ignore the added cost of creating a new string for each comparison (which is minimal if you're only doing one or two comparisons).

A new way to do this. iOS 8

let string: NSString = "Café"
let substring: NSString = "É"

string.localizedCaseInsensitiveContainsString(substring) // true

- (NSComparisonResult)caseInsensitiveCompare:(NSString *)aString

Try this method

- (NSComparisonResult)caseInsensitiveCompare:(NSString *)aString

Converting Jason Coco's answer to Swift for the profoundly lazy :)

if ("Some String" .caseInsensitiveCompare("some string") == .OrderedSame)
{
  // Strings are equal.
}

to check with the prefix as in the iPhone ContactApp

([string rangeOfString:prefixString options:NSCaseInsensitiveSearch].location == 0)

this blog was useful for me

Alternate solution for swift:

To make both UpperCase:

e.g:

if ("ABcd".uppercased() == "abcD".uppercased()){
}

or to make both LowerCase:

e.g:

if ("ABcd".lowercased() == "abcD".lowercased()){
}

On macOS you can simply use -[NSString isCaseInsensitiveLike:], which returns BOOL just like -isEqual:.

if ([@"Test" isCaseInsensitiveLike: @"test"])
    // Success

NSMutableArray *arrSearchData;  
NSArray *data=[arrNearByData objectAtIndex:i];
NSString *strValue=[NSString stringWithFormat:@"%@", [data valueForKey:@"restName"]];
NSRange r = [strValue rangeOfString:key options:NSCaseInsensitiveSearch];

if(r.location != NSNotFound)
{
     [arrSearchData addObject:data];
}