5/7/15 - File Manager UI Improvements

In order to prepare for the Career Center Tech Expo, I hammered out some improvements to our rudimentary file interface.  Before, the app would display all the files on the (emulated) SD card, which for some reason included a bunch of temp files for the emulator.  I first added logic to only show files with paths that matched the regular expression /librifox\/.*/, which only shows files that have librifox/ in the path. Next, I refactored our enumeration handler by pulling all the file traversal logic into a base method that takes functions func_each for code to be executed for each match, func_done for code to be executed once all the files had been traversed, and func_error for any errors that occurred.

This is a really flexible way to implement an algorithm that has slight variations in how it works, as I can display all the librifox files in a list view and delete all librifox files with the exact same call pattern, just by varying the functions passed as func_each and func_done.

Also, because functions keep the scope they were originally called by, I was able to do the following to check whether any librifox files were present on the device:

	// adapted from displayAppFiles() in app.js
	function checkIfAnyFiles() {
	var items_found = 0; // variable defined in outer function
	var each_item = function(result) {
	items_found++; // still in scope for the callback
	}
	var when_done = function () {
	// Output depends on number of items traversed by each_item
	console.log('found ' + items_found + ' files');
	if (items_found == 0) {
	// ... write 'no files found' to the listview
	}
	}
	enumerateFiles({ // ... ,
	func_each: each_item, // functions are only called inside #enumerateFiles
	func_done: when_done
	});
	}

view raw js_callback_scope_ex.js hosted with ❤ by GitHub

I'm really glad I'm reading JavaScript: the Good Parts :)

---

I thought that this was something unique to javascript, but it works in ruby as well! Neat!

	class TestClass
	def test_scope
	times_called = 0
	other_func do # passes block into #other_func
	times_called += 1
	end
	puts "Called #{times_called} times"
	end
	end
	def other_func(&callback)
	(1..5).each do
	callback.call
	end
	end
	tc = TestClass.new
	tc.test_scope #=> Called 5 times

view raw scope_ruby_ex.rb hosted with ❤ by GitHub