[ios] 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)

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

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.

- (NSComparisonResult)caseInsensitiveCompare:(NSString *)aString

to check with the prefix as in the iPhone ContactApp

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

this blog was useful for me

 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
 }

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()){
}

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];
}

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

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

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.
}