Tutorial by Examples

The text binding can be used with any element to update it's innerText. <p> <span data-bind="text: greeting"></span>, <span data-bind="text: subject"></span>. </p> ko.applyBindings({ greeting: ko.observable("Hello"), ...

When is an IComparer<T> a subtype of a different IComparer<T1>? When T1 is a subtype of T. IComparer is contravariant in its T parameter, which means that IComparer's subtype relationship goes in the opposite direction as T's. class Animal { /* ... */ } class Dog : Animal { /* ... */ }...

Folds are (higher-order) functions used with sequences of elements. They collapse seq<'a> into 'b where 'b is any type (possibly still 'a). This is a bit abstract so lets get into concrete practical examples. Calculating the sum of all numbers In this example, 'a is an int. We have a list of...

let x = true match x with | true -> printfn "x is true" yields a warning C:\Program Files (x86)\Microsoft VS Code\Untitled-1(2,7): warning FS0025: Incomplete pattern matches on this expression. For example, the value 'false' may indicate a case not covered by the pattern(s). ...

Incorrect usage: In the following snippet, the last match will never be used: let x = 4 match x with | 1 -> printfn "x is 1" | _ -> printfn "x is anything that wasn't listed above" | 4 -> printfn "x is 4" prints x is anything that wasn't listed abov...

type Person = { Age : int PassedDriversTest : bool } let someone = { Age = 19; PassedDriversTest = true } match someone.PassedDriversTest with | true when someone.Age >= 16 -> printfn "congrats" | true -> printfn "wait until you are 16" | false -> p...

Returns a string that represents the unqualified name of a variable, type, or member. int counter = 10; nameof(counter); // Returns "counter" Client client = new Client(); nameof(client.Address.PostalCode)); // Returns "PostalCode" The nameof operator was introduced in C# ...

>>> code = """for i in range(5):\n print('Hello world!')""" >>> exec(code) Hello world! Hello world! Hello world! Hello world! Hello world!

>>> expression = '5 + 3 * a' >>> a = 5 >>> result = eval(expression) >>> result 20

compile built-in function can be used to precompile an expression to a code object; this code object can then be passed to eval. This will speed up the repeated executions of the evaluated code. The 3rd parameter to compile needs to be the string 'eval'. >>> code = compile('a * b + c', '&l...

>>> variables = {'a': 6, 'b': 7} >>> eval('a * b', globals=variables) 42 As a plus, with this the code cannot accidentally refer to the names defined outside: >>> eval('variables') {'a': 6, 'b': 7} >>> eval('variables', globals=variables) Traceback (most ...

You can fetch the current properties of the Annotation by using Reflection to fetch the Method or Field or Class which has an Annotation applied to it, and then fetching the desired properties. @Retention(RetentionPolicy.RUNTIME) @interface MyAnnotation { String key() default "foo";...

As the static keyword is used for accessing fields and methods without an instantiated class, it can be used to declare constants for use in other classes. These variables will remain constant across every instantiation of the class. By convention, static variables are always ALL_CAPS and use unders...

Static gives a method or variable storage that is not allocated for each instance of the class. Rather, the static variable is shared among all class members. Incidentally, trying to treat the static variable like a member of the class instance will result in a warning: public class Apple { pu...

It is possible to create a QtQuick view directly from C++ and to expose to QML C++ defined properties. In the code below the C++ program creates a QtQuick view and exposes to QML the height and width of the view as properties. main.cpp #include <QApplication> #include <QQmlContext> #...

If you want to mock AR that doesn't try to connect to database you can do it in the following way (if using PHPUnit): $post = $this->getMockBuilder('\app\model\Post') ->setMethods(['save', 'attributes']) ->getMock(); $post->method('save')->willReturn(true); $post->meth...

Jagged arrays are arrays that instead of primitive types, contain arrays (or other collections). It's like an array of arrays - each array element contains another array. They are similar to multidimensional arrays, but have a slight difference - as multidimensional arrays are limited to a fixed nu...

The Application directive defines application-specific attributes. It is provided at the top of the global.aspx file. The basic syntax of Application directive is: <%@ Application Language="C#" %> The attributes of the Application directive are: AttributesDescriptionInheritsThe...

The control directive is used with the user controls and appears in the user control (.ascx) files. The basic syntax of Control directive is: <%@ Control Language="C#" EnableViewState="false" %> The attributes of the Control directive are: AttributesDescriptionAutoEv...

The Implement directive indicates that the web page, master page or user control page must implement the specified .Net framework interface. The basic syntax for implements directive is: <%@ Implements Interface="interface_name" %>