Add callback function to handle switching tabs in multi-tab apps

[crew102]

• Should close #17.
• Example usage can be found at inst/examples/switchTabs.R
• This solution should work when needing to switch menuitems in shinydashboards as well, though I didn't test this.

[carlganz]

@crew102 thanks for taking the time to work on this. I think the file manipulation, and text parsing in readCallback and getJSfunBody are way outside the scope of what this package should do.

When I get some free time I will integrate the switchTabs function you provided. Thank you very much for the contribution.

[crew102]

Hi @carlganz , readCallback() just reads in a callback function defined in inst/javascript/callbacks - it doesn't really add much scope to the package...and getJSfunBody() is just a helper function (it's not exported), so I don't see how that adds scope either.

I assume you are thinking of just putting the body of the switchTab() function in an R string and exporting that for users? The reason why I chose to have readCallback() as the public API for the functionality added in switchTab() instead of just exporting a string was a) I generally think that different languages shouldn't be mixed in the same source code file if you can help it (hence the rationale for reading in a javascript file), and b) I think it will be easier for interested users to understand what switchTab() actually does if it appears in its full form.

[carlganz]

Merged, thanks for taking time to contribute.