Re: Calculating a total from a collection of numeric attributes
Re: Calculating a total from a collection of numeric attributes
- Subject: Re: Calculating a total from a collection of numeric attributes
- From: Ian Piper <email@hidden>
- Date: Sun, 18 Oct 2009 18:16:13 +0100
On 18 Oct 2009, at 15:45, I. Savant wrote:
On Oct 17, 2009, at 7:40 PM, Ian Piper wrote:
I have a Core Data entity that has an attribute called charge
(stored as a float). So I am storing a number of records each of
which has a charge. I simply want to be able to show a running
total of charges as I add or remove items. I was hoping that I
might be able to use a simple binding for this: I created a label
and thought I might be able to bind its value to array
controller.arrangedObjects.charge.sum or something like that. No
luck though.
I cannot see anything in the documentation or from searches. Can
anyone point me towards either examples or documentation?
You want set and array operators:
http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/KeyValueCoding/Concepts/ArrayOperators.html
You really should read the KVC, KVO, Bindings, and Core Data guides
front to back since there are terms you wouldn't otherwise know to
search for. It's best to know you read about something but forget
the specifics then to not read it at all and have no idea. :-)
Thanks for the reply. Since posting the message I found and read those
documents and have that chapter open on my desktop right now. In case
anyone else wants to do something similar the simplest description of
the answer is to set a binding for the label like this:
[name of array controller]email@hiddene
Ian.
--
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