Tutorial by Examples: ch

Some example cases when the result is an optional. var result: AnyObject? = someMethod() switch result { case nil: print("result is nothing") case is String: print("result is a String") case _ as Double: print("result is not nil, any value that is a Dou...

A common use for enumerators is for switch statements and so they commonly appear in state machines. In fact a useful feature of switch statements with enumerations is that if no default statement is included for the switch, and not all values of the enum have been utilized, the compiler will issue ...

Pattern matching allows to deconstruct complex values and it is by no way limited to the “outer most” level of the representation of a value. To illustrate this, we implement the function transforming a boolean expression into a boolean expression where all negations are only on atoms, the so calle...

Pattern matching can be used to deconstruct records. We illustrate this with a record type representing locations in a text file, e.g. the source code of a program. type location = { filename : string; line: int; column: int; offset: int; } A value x of type location can be deconstr...

You can use the is operator to validate whether a value is of a certain type: var sprite:Sprite = new Sprite(); trace(sprite is Sprite); // true trace(sprite is DisplayObject); // true, Sprite inherits DisplayObject trace(sprite is IBitmapDrawable); // true, DisplayObject implements IBitmapDra...

This example uses a search controller to filter the data inside a table view controller. The search bar is placed inside the navigation bar that the table view is embedded into. Embed a UITableViewController into a UINavigationController to get the UINavigationItem (which contains the navigation ...

This example uses a search controller to filter the cells in a table view controller. The search bar is placed inside the header view of the table view. The table view content is offset with the same height as the search bar so that the search bar is hidden at first. Upon scrolling up past the top e...

Undo changes to a file or directory in the working copy. git checkout -- file.txt Used over all file paths, recursively from the current directory, it will undo all changes in the working copy. git checkout -- . To only undo parts of the changes use --patch. You will be asked, for each chang...

It is considered good practice to use a prefix when creating git archives, so that extraction will place all files inside a directory. To create an archive of HEAD with a directory prefix: git archive --output=archive-HEAD.zip --prefix=src-directory-name HEAD When extracted all the files will be...

It is also possible to create archives of other items than HEAD, such as branches, commits, tags, and directories. To create an archive of a local branch dev: git archive --output=archive-dev.zip --prefix=src-directory-name dev To create an archive of a remote branch origin/dev: git archive --...

With git archive it is possible to create compressed archives of a repository, for example for distributing releases. Create a tar archive of current HEAD revision: git archive --format tar HEAD | cat > archive-HEAD.tar Create a tar archive of current HEAD revision with gzip compression: gi...

This hook works similarly to the post-commit hook, but it's called whenever you successfully check out a reference with git checkout. This could be a useful tool for clearing out your working directory of auto-generated files that would otherwise cause confusion. This hook accepts three parameters:...

git diff branch1..branch2

Sometimes you just need a diff to apply using patch. The regular git --diff does not work. Try this instead: git diff --no-prefix > some_file.patch Then somewhere else you can reverse it: patch -p0 < some_file.patch

You can use an environment filter to change the author of commits. Just modify and export $GIT_AUTHOR_NAME in the script to change who authored the commit. Create a file filter.sh with contents like so: if [ "$GIT_AUTHOR_NAME" = "Author to Change From" ] then export GIT_A...

Example method in controller @RequestMapping(value = "/test") public String showCheckbox(Model model) { boolean myBooleanVariable = false; model.addAttribute("myBooleanVariable", myBooleanVariable); return "sample-checkbox"; } View: sample-checkbox....

You may want to nest cached fragments inside other cached fragments. This is called Russian doll caching. The advantage of Russian doll caching is that if a single product is updated, all the other inner fragments can be reused when regenerating the outer fragment. As explained in the previous sec...

Query caching is a Rails feature that caches the result set returned by each query. If Rails encounters the same query again for that request, it will use the cached result set as opposed to running the query against the database again. For example: class ProductsController < ApplicationControl...

If you need to search an ActiveRecord model for similar values, you might be tempted to use LIKE or ILIKE but this isn't portable between database engines. Similarly, resorting to always downcasing or upcasing can create performance issues. You can use ActiveRecord's underlying Arel matches method...

Picasso.with(context) .load(uri) .networkPolicy(NetworkPolicy.NO_CACHE) .memoryPolicy(MemoryPolicy.NO_CACHE) .placeholder(R.drawable.placeholder) .into(imageView);