Re: Custom NSFormatter classes
Re: Custom NSFormatter classes
- Subject: Re: Custom NSFormatter classes
- From: Patrick Mau <email@hidden>
- Date: Sun, 03 Jan 2010 12:58:29 +0100
Hallo Henri
Your assumption about how formatters should work are correct. To provide a useful answer
I have setup a mini project here, because I have stumbled over a detail I did not now:
http://public.me.com/pmau
I took your approach and implemted a minimal datasource and a "Foo" object.
This is not a great example, but here's what II did not know:
When you wire up the formatter to the text field cell in IB,
"setFormatter" is called on the TextFieldCell, which in turn will
call your formatting code withe the cell's title:
run
[Switching to process 7123]
Running…
2010-01-03 12:39:47.790 Formatter[7123:a0f] NSCFString Cell Title
2010-01-03 12:39:47.810 Formatter[7123:a0f] Foo <Foo: 0x1139291d0>
2010-01-03 12:39:47.811 Formatter[7123:a0f] Foo <Foo: 0x1151000a0>
2010-01-03 12:39:47.811 Formatter[7123:a0f] Foo <Foo: 0x1151000b0>
Therefore you have too prepare to receive at least one object, which is not "Foo".
Interestingly, I could not find that little detail in the documentation.
If you want to return an instance Foo from your datasource, it is much more convenient to write
your own NSCell subclass, because you can control editing and formatting much easier.
You can even use an attached formatter that you setup in IB, passing it a property of Foo.
All the best,
Patrick
On Jan 3, 2010, at 1:47 , Henri Häkkinen wrote:
> Hello.
>
> I have an array of custom Foo objects which I would need to display in an NSTableView object. I implement the data source delegate like this:
>
> - (NSInteger)numberOfRowsInTableView:(NSTableView *)tableView {
> return [arrayOfFoos count];
> }
>
> - (id)tableView:(NSTableView *)tableView objectValueForTableColumn:(NSTableColumn *)tableColumn row:(NSInteger) row {
> return [arrayOfFoos objectAtIndex:row];
> }
>
> Then I have NSFormatter subclass FooFormatter which takes in a Foo object and converts it to a string. This formatter object is attached to the formatter property of the TextFieldCell class in the NSTableView's table column. The FooFormatter is like this:
>
> @implementation FooFormatter
>
> - (NSString *)stringForObjectValue:(id)anObject {
> if ([anObject isKindOfClass:[Foo class]] == NO) {
> [NSException raise:NSInvalidArgumentException format:@"Wrong object"];
> }
> Foo *foo = (Foo *)anObject;
> NSString *string;
> // ... convert foo into string ...
> return string;
> }
>
> @end
>
> I am assuming here that the object returned by the data source objectValueForTableColumn: is passed to the formatter's stringForObjectValue: before it is displayed in the text field cell -- this seems not to be the case. I would like to keep formatting of Foo objects separate from the data source (if possible) since I intend to implement multiple different FooFormatter derived classes suited for different situations.
>
> The Cocoa docs seem to be a little low on details on how these NSFormatter objects are supposed to work. Can anybody give me any insight? Would be appreciated. Thanks.
>
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