[aerogear-dev] Client Paging Strawman

[Summers Pittman]

On 01/14/2013 01:00 PM, Kris Borchers wrote:
> OK folks, below is the contents of this gist 
> https://gist.github.com/4531575. I may have missed a number of things, 
> gotten too specific in places or not specific enough in others. This 
> should hopefully get a good discussion going on how we want to handle 
> paging across all of the client libraries. Let's keep all comments on 
> the list and not the gist as much as possible to avoid breaking up the 
> conversation.
>
> Below is a pipe configuration showing the different paging options. 
> Defaults are just suggestions and are up for discussion as much as the 
> rest of it
>
>     var pagedPipe = AeroGear.Pipeline({
>         name: "pager",
>         settings: {
>             paged: {String}, // Default is "headers", can also be 
> "content", or undefined for no paging
>             pageConfig: { // Only required if paged is not undefined
>                 // which page, header default is "AG-Paging-Offset", 
> content default is "paging.offset"
>                 offset: {String},
>                 offsetVal: {Number}, // Default 0 for first page
>                 // items per page, header default is 
> "AG-Paging-Limit", content default is "paging.limit"
>                 limit: {String},
>                 limitVal: {Number}, // Default 5 items per page
>                 // total number of items, header default is 
> "AG-Paging-Total", content default is "paging.total"
>                 total: {String},
>                 // link to next page, default in both cases is undefined
>                 next: {String},
>                 // link to previous page, default in both cases is 
> undefined
>                 prev: {String}
>             }
>         }
>     }).pipes.pager;
>
> Getter/Setter methods should be provided for getting and updating the 
> offsetVal and limitVal defaults
>
>     var defaultOffset = pagedPipe.getOffsetVal();
>     pagedPipe.setOffsetVal( defaultOffset + 1 ); // by default the 
> second page would be returned
>     var defaultLimit = pagedPipe.getLimitVal();
>     pagedPipe.setLimitVal( defaultLimit + 5 ); // by default, 10 items 
> would be returned per page
>
> ## read()
> By default, a read() against a paged pipe will return the first page 
> based on the default offsetVal and limitVal. We could possible add an 
> option that doesn't effect unpaged pipes but on a paged pipe, it can 
> be used to turn off paging for that read() and get all data
>
>     // Get first page
>     pagedPipe.read({success callback handles data});
>     // Get all data from paged pipe
>     pagedPipe.read({
>         page: false,
>         success: handle the data
>     });
> To avoid code duplication, **next**, **prev**, **first** and **last** 
> pages can be retrieved by passing an option to the read method of a 
> paged pipe since other than some paging housekeeping, the code would 
> be the same. We can also use that same option as above that was used 
> to get all data from a paged pipe. One question, when requesting prev 
> from first page or next from last page, should it throw an error that 
> needs to be handled or just return and empty data set? I see 
> advantages and disadvantages of both.
>
>     // Get next page
>     pagedPipe.read({
>         page: "next",
>         success: handle the data
>     });
>     // Get previous page
>     pagedPipe.read({
>         page: "prev",
>         success: handle the data
>     });
>     // Get first page
>     pagedPipe.read({
>         page: "first",
>         success: handle the data
>     });
>     // Get last page
>     pagedPipe.read({
>         page: "last",
>         success: handle the data
>     });
>
>
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At first glance I don't like having the distinction between a "Pipe" and 
a "PagedPipe".  In Java land PagedPipe will be an interface which 
extends Pipe (this is no big deal) and PagedRestAdatper would extend 
RestAdapted and implement PagedPipe.  This isn't too bad but it makes 
reusing paging logic a bit harder.  (And also this is at first glance).

The biggest issue I see with a PagedPipe is it means a developer can't 
change his paging preferences without creating a new Pipe.

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