Suppose you have a network method that only uses a single block callback
typedef void (^Handler)(BOOL success, id response, NSError *error);
- (void)makeRequestWithHandler:(Handler)handler;
But you have to make this request dozens of times, and you want to reuse the same failure handler in most cases? Easy, just have a factory function that returns a block:
typedef void (^SuccessHandler)(id response);
typedef void (^ErrorHandler)(NSError *error);
Last time I showed you one strategy for trimming the fat from our view controller by seperating out protocols. In part 2 of this 3 part series we are going to use an architecture known as MVVM to dumb down our view controller. View controllers are usually filled with business rules, this is a problem for a number of reasons, two of which being:
MVVM stands for Model View ViewModel and is just a way of describing how to break up your interface, business rules and data so that they flow together in a logical, but seperated, way.
This is what that flow looks like
I hate to say it but our view controllers have gotten fat, and it's our fault! We feed them protocol after protocol, business rule after business rule. They don't know any better and they just gobble them all up...
This will be a 3 part "Tune up your table view" series in which we will take an old fat view controller, slim it down with some refactoring, freshen it up with some MVVM and then make it fly with some better asynchronous operation management!
In part 1 using refactoring and a couple of Interface Builder tricks hopefully I can provide some motivation to start your journey towards getting your view controllers back in fighting shape!
UITableViews are pretty integral to most iOS apps so I'm going to use it as an example of how to change a 'fat' view controller into a 'slim' one.
Welcome back for the conclusion of this 3 part series! In part 1 we learnt how to slim down our view controllers to a manageable size. In part 2 we learnt how to strip out all the non-ui related logic. This time we are going to focus solely on the UITableView and how we can properly handle multiple asynchronous operations in its cells for maximum performance!
As always we will be starting with our project from last time.
Our current implementation is very bad... our UITableViewCells are performing an expensive operation, and on the main thread no less!
The following code is currently in the setup method of our cell:
Looking for a mentor in iOS?- try this post: http://stephaniehurlburt.com/blog/2016/11/14/list-of-engineers-willing-to-mentor-you
| [alias] | |
| verbs = !git log --pretty=format:'%s' | cut -d \" \" -f 1 | sort | uniq -c | sort -nr |
| exec > /tmp/${PROJECT_NAME}_archive.log 2>&1 | |
| UNIVERSAL_OUTPUTFOLDER=${BUILD_DIR}/${CONFIGURATION}-universal | |
| if [ "true" == ${ALREADYINVOKED:-false} ] | |
| then | |
| echo "RECURSION: Detected, stopping" | |
| else | |
| export ALREADYINVOKED="true" |
| extension Collection { | |
| func eachConsecutive(_ size: Int) -> Array<SubSequence> { | |
| let droppedIndices = indices.dropFirst(size - 1) | |
| return zip(indices, droppedIndices) | |
| .map { return self[$0...$1] } | |
| } | |
| } |
| //This is the swift version of the following gist by @shexbeer https://gist.github.com/shexbeer/cb069d36ca8ec5edb515 | |
| func cropCameraImage(original: UIImage, previewLayer: AVCaptureVideoPreviewLayer) -> UIImage? { | |
| var image = UIImage() | |
| let previewImageLayerBounds = previewLayer.bounds | |
| let originalWidth = original.size.width | |
| let originalHeight = original.size.height | |
| # expand_path is genuine and DOES KNOW ABOUT absolute and relative paths | |
| File.expand_path('relative/path/to/dir_or_file', '/start/path') # "/start/path/relative/path/to/dir_or_file" | |
| File.expand_path('../application', __FILE__) # "/absolute/path/to/FILE/../application" | |
| File.expand_path('/path/to/dir_or_file', '/start/path') # "/path/to/dir_or_file" | |
| File.expand_path('../path/to/dir_or_file', '/start/path') # "/start/path/to/dir_or_file" | |
| # join seems to be STUPID. It just joins strings (and adds file separator if needed) | |
| File.join('some/path/', '/other/path.rb') # "some/path/other/path.rb" | |
| # modify the global load path: |