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Limit input to NSTextField

I want to restrict character input to NSTextField

, i.e. so that forbidden characters don't even appear. Most of what I have found on this topic are solutions that are only tested after completing text input or using NSFormatter

that still allows the character to be displayed.

So far I have come up with this solution, subclassing NSTextField

:

class RestrictedTextField : NSTextField
{
    static let VALID_CHARACTERS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890'-.& ";

    override func textDidChange(notification:NSNotification)
    {
        for c in stringValue
        {
            if (RestrictedTextField.VALID_CHARACTERS.rangeOfString("\(c)") == nil)
            {
                stringValue = stringValue.stringByReplacingOccurrencesOfString("\(c)", withString: "", options: .LiteralSearch, range: nil);
                break;
            }
        }
    }
}

It works, but it's actually not optimal because the text cursor still moves one place if it tries to enter an invalid character. I also think that the loop is unnecessary, so I am wondering if anyone knows a more elegant solution for this?

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1 answer


You have complete control with the subclass NSFormatter

. I'm not sure why you think not.

Replace isPartialStringValid(_:proposedSelectedRange:originalString:originalSelectedRange:errorDescription:)

and implement the desired logic. From the docs (with some minor changes from me):



In the subclass implementation, evaluate [the pointed string *partialStringPtr

] according to the context. Return YES

if partialStringPtr

applicable and NO

if partialStringPtr

not acceptable. Assign a new line partialStringPtr

and a new range before proposedSelRangePtr

and return NO

if you want to replace the line and change the selection range.

So, if a user tries to insert forbidden characters, you can either reject editing them entirely, or modify it to remove those forbidden characters. (Remember that custom changes can involve insertion, so it doesn't have to be just one typed character.) To reject the change entirely, assign origString

to *partialStringPtr

and origSelRange

to *proposedSelRangePtr

.

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