Tutorial by Examples: clos

Since PHP7, it is possible to bind a closure just for one call, thanks to the call method. For instance: <?php class MyClass { private $property; public function __construct($propertyValue) { $this->property = $propertyValue; } } $myClosure = function() ...

In general, an observer is a class with a specific method being called when an action on the observed object occurs. In certain situations, closures can be enough to implement the observer design pattern. Here is a detailed example of such an implementation. Let's first declare a class whose purpos...

def addNumbers = { a, b -> a + b } addNumbers(-7, 15) // returns 8

['cat', 'dog', 'fish'].collect { it.length() } it is the default name of the parameter if you have a single parameter and do not explicitly name the parameter. You can optionally declare the parameter as well. ['cat', 'dog', 'fish'].collect { animal -> animal.length() }

A Closure is a function taken together with an environment. The function is typically an anonymous function defined inside another function. The environment is the lexical scope of the enclosing function (very basic idea of a lexical scope of a function would be the scope that exists between the fun...

When we are finished querying the database, it is recommended to close the connection to free up resources. Object oriented style $conn->close(); Procedural style mysqli_close($conn); Note: The connection to the server will be closed as soon as the execution of the script ends, unless it...

Using functions that take in and execute closures can be extremely useful for sending a block of code to be executed elsewhere. We can start by allowing our function to take in an optional closure that will (in this case) return Void. func closedFunc(block: (()->Void)? = nil) { print("...

A closure can be defined with a typealias. This provides a convenient type placeholder if the same closure signature is used in multiple places. For example, common network request callbacks or user interface event handlers make great candidates for being "named" with a type alias. public...

Functions remember the lexical scope they where defined in. Because of this, we can enclose a lambda in a let to define closures. (defvar *counter* (let ((count 0)) (lambda () (incf count)))) (funcall *counter*) ;; => 1 (funcall *counter*) ;; = 2 In the example above,...

do local tab = {1, 2, 3} function closure() for key, value in ipairs(tab) do print(key, "I can still see you") end end closure() --> 1 I can still see you --> 2 I can still see you --> 3 I can still see you end ...

A method can be converted to a closure using the & operator. def add(def a, def b) { a + b } Closure addClosure = this.&add assert this.add(4, 5) == addClosure(4, 5)

context.closePath() Draws a line from the current pen location back to the beginning path coordinate. For example, if you draw 2 lines forming 2 legs of a triangle, closePath will "close" the triangle by drawing the third leg of the triangle from the 2nd leg's endpoint back to the firs...

class MyHello { def sayHello() { "Hello, world" } } def cl = { sayHello() } cl() // groovy.lang.MissingMethodException cl.delegate = new MyHello() cl(); // "Hello, world" Used extensively by Groovy DSLs.

Most streams must be closed when you are done with them, otherwise you could introduce a memory leak or leave a file open. It is important that streams are closed even if an exception is thrown. Java SE 7 try(FileWriter fw = new FileWriter("outfilename"); BufferedWriter bw = new Buf...

public final class DrawerLayoutTest { @Test public void Open_Close_Drawer_Layout() { onView(withId(R.id.drawer_layout)).perform(actionOpenDrawer()); onView(withId(R.id.drawer_layout)).perform(actionCloseDrawer()); } public static ViewAction actionOpenDrawer() { return ne...

zo opens a fold underneath the cursor. zO opens all folds underneath the cursor, recursively. zc closes a fold underneath the cursor. zC closes all folds underneath the cursor, recursively. za toggles a fold under the cursor (a closed fold is opened, an opened fold is closed). zM closes all f...

You may have noticed that many applications have double-back-click functionality to exit the app. In this example, we are overriding the default back button action using the onBackPressed() method override. This method will Toast a message for the single back-click action, and will close the app if...

Instead of using the delegate pattern, that split the implementation in various part of the UIViewController class, you can even use closures to pass data back and forward. By assuming that you're using the UIStoryboardSegue, in the prepareForSegue method you can easily setup the new controller in ...

A lambda closure is created when a lambda expression references the variables of an enclosing scope (global or local). The rules for doing this are the same as those for inline methods and anonymous classes. Local variables from an enclosing scope that are used within a lambda have to be final. Wit...

A stream is closed by sending a closing </stream> tag. After the closing stream tag is sent, no more data should be sent on the stream (even in response to data received from the other party). Before closing the connection, the sending entity should wait for a response </stream> tag to g...