Question: Signal for unique values only

[fatuhoku]

I want to filter values based on the Suppose I have a signal

RACSignal *original = ...;   // sends values [1,1,2,2,3,3,3,3,3,3,3,4,4,4,3,3,1,2]

How can I create a signal filtered such that it sends values of s only if it's changed from the previous value? i.e.

RACSignal *filtered = [original ...];  // sends values [1, 2, 3, 4, 3, 1, 2]

My RAC intuition tells me I can do this with one of those mapWithPrevious: or whatever methods, but I'm not very sure how they're used.

[jspahrsummers]

-[RACSignal distinctUntilChanged]

[fatuhoku]

Top notch response time. Thank you @jspahrsummers =]

[conradwt]

@jspahrsummers Would it a good idea to add this Q/A to the filtering or appropriate section of the online documentation?

[jspahrsummers]

The operator itself is documented, and it's used in a lot of examples and past Q&A. I'm not sure where else we could fit it in.

[fatuhoku]

Well I hope this question and answer serves as documentation enough that users looking for 'unique values' will be pointed to this very useful operator.

[wdcurry]

new to RAC, liking its potential, totally not getting the context of the name "distinctUntilChanged" .. It almost seems like it needs to be oppositely named. As it returned a distinct value when the the value changes to another value, it might actually be distinctWhenChanged. I can learn to understand it of course, but is ain't intuitive.

[jspahrsummers]

@wdcurry The Swift API calls it skipRepeats instead.

[wdcurry]

Thanks @jspahrsummers .. now that is more immediately understandable..