NSString value validation in iOS - iphone

Question

This simple validation method for NSString makes trouble.
I have an NSString value and I want to validate the string, i.e, if the string contains only 'a to z' (or) 'A to Z' (or) '1 to 9' (or) '#,!,&' then the string is valid. If the string contains any other values then this the NSString is invalid, how can i validate this..?
As example:
Valid:
NSString *str="aHrt#2"; // something like this
Invalid:
NSString *str="..gS$"; // Like this

Answer 1

Try using character sets:
NSMutableCharacterSet *set = [NSMutableCharacterSet characterSetWithCharactersInString:#"#!&"];
[set formUnionWithCharacterSet:[NSCharacterSet alphanumericCharacterSet]];
if ([string rangeOfCharacterFromSet:[set invertedSet]].location == NSNotFound) {
// contains a-z, A-Z, 0-9 and &#! only - valid
} else {
// invalid
}

Answer 2

I would do something using stringByTrimmingCharactersInSet
Create an NSCharacterSet containing all valid characters, then trim those characters from the test string, if the string is now empty it is valid, if there are any characters left over, it is invalid
NSCharacterSet *validCharacters = [NSCharacterSet characterSetWithCharactersInString:#"myvalidchars"];
NSString *trimmedString = [testString stringByTrimmingCharactersInSet:validCharachters];
BOOL valid = [trimmedString length] == 0;
Edit:
If you want to control the characters that can be entered into a text field, use textField:shouldChangeCharactersInRange:replacementString: in UITextFieldDelegate
here the testString variable becomes the proposed string and you return YES if there are no invalid characters

Answer 3

The NSPredicate class is what you want
More info about predicate programming. Basically you want "self matches" (your regular expression). After that you can use the evaluateWithObject: method.
EDIT Easier way: (nevermind, as I am editing it wattson posted what I was going to)

Answer 4

You can use the class NSRegularExpression to do this.
https://developer.apple.com/library/mac/documentation/Foundation/Reference/NSRegularExpression_Class/Reference/Reference.html

Answer 5

You can also use NSRegularExpression to search your NSString, if it contains only the valid characters (or vice versa).
More info:
Search through NSString using Regular Expression
Use regular expression to find/replace substring in NSString

Answer 6

- (BOOL)validation:(NSString *)string
{
NSCharacterSet *cs = [[NSCharacterSet characterSetWithCharactersInString:#"1234567890abcdefghik"] invertedSet];
NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:#""];
return ([string isEqualToString:filtered]);
}
In your button action:
-(IBAction)ButtonPress{
if ([self validation:activity.text]) {
NSLog(#"Macth here");
}
else {
NSLog(#"Not Match here");
}
}
Replace this "1234567890abcdefghik" with your letters with which you want to match

Answer 7

+(BOOL) validateString: (NSString *) string
{
NSString *regex = #"[A-Z0-9a-z#!&]";
NSPredicate *test = [NSPredicate predicateWithFormat:#"SELF MATCHES %#", emailRegex];
BOOL isValid = [test evaluateWithObject:string];
return isValid;
}

Answer 8

You can simply do it using NSMutableCharacterSet
NSMutableCharacterSet *charactersToKeep = [NSMutableCharacterSet alphanumericCharacterSet];
[charactersToKeep addCharactersInString:#"#?!"];
NSCharacterSet *charactersToRemove = [charactersToKeep invertedSet]
NSString *trimmed = [ str componentsSeparatedByCharactersInSet:charactersToRemove];
if([trimmed length] != 0)
{
//invalid string
}
Reference NSCharacterSet

Answer 9

You can use regex. If every thing fails use brute force like
unichar c[yourString.length];
NSRange raneg={0,2};
[yourString getCharacters:c range:raneg];
// now in for loop
for(int i=0;i<yourString.length;i++)
{
if((c[i]>='A'&&c[i]<='Z')&&(c[i]=='#'||c[i]=='!'||c[i]=='&'))
{
//not the best or most efficient way but will work till you write your regex:P
}
}