Re: Unusual Conditional Formatting
Re: Unusual Conditional Formatting
- Subject: Re: Unusual Conditional Formatting
- From: Jonathan Mitchell <email@hidden>
- Date: Wed, 07 Sep 2016 10:25:48 +0100
A couple of suggestions.
> Here is what I have so far: I used a category on NSNumber to add a "valueType" attribute as described at http://nshipster.com/associated-objects/.
>
> The formatter checks this and the user preference when formatting an incoming value. It sets some instance variables on itself to remember what it last saw so that it can correctly default its interpretation of an entered value when trying to send it back.
>
On your associated object setter add KVO support.
- (void)setValueType:(int)valueType
{
[self willChangeValueForKey:@"valueType"];
objc_setAssociatedObject(self, @selector(valueType), @(valueType), OBJC_ASSOCIATION_RETAIN);
[self didChangeValueForKey:@"valueType"];
}
> The binding for the values is indirect - to the effect of "myThing.value" - and if I change "myThing" but the new thing has the same numeric value, the formatter does not always seem to trigger to render the value in the correct format - it holds that of the previous thing. If I change the value from another control, when the bindings update the field, the formatting is suddenly corrected.
The formatter will only receiver the value part of “myThing.value”.
It may well be that the formatter doesn’t re-format because the actual value doesn’t change - formatting may be an expensive operation.
In this case you may want to reformat so:
1. consider Manual triggering of reformat if valueType changes.
2. Try overriding NSFormatter -stringForObjectValue: - that should give you a low enough foothold into the rendering.
HTH
J
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