Tutorial by Examples: l

What is Bool?

Bool is a Boolean type with two possible values: true and false. let aTrueBool = true let aFalseBool = false Bools are used in control-flow statements as conditions. The if statement uses a Boolean condition to determine which block of code to run: func test(_ someBoolean: Bool) { if som...

Swift Language • Booleans

Negate a Bool with the prefix ! operator

The prefix ! operator returns the logical negation of its argument. That is, !true returns false, and !false returns true. print(!true) // prints "false" print(!false) // prints "true" func test(_ someBoolean: Bool) { if !someBoolean { print("someBoolean ...

Swift Language • Booleans

Finding out the Number of Elements in an Array

NSArray *myColors = [NSArray arrayWithObjects: @"Red", @"Green", @"Blue", @"Yellow", nil]; NSLog (@"Number of elements in array = %lu", [myColors count]);

Objective-C Language • NSArray

Adding elements

NSMutableArray *myColors; myColors = [NSMutableArray arrayWithObjects: @"Red", @"Green", @"Blue", @"Yellow", nil]; [myColors addObject: @"Indigo"]; [myColors addObject: @"Violet"]; //Add objects from an NSArray NSArray *myArray = @[@...

Objective-C Language • NSMutableArray

Insert Elements

NSMutableArray *myColors; int i; int count; myColors = [NSMutableArray arrayWithObjects: @"Red", @"Green", @"Blue", @"Yellow", nil]; [myColors insertObject: @"Indigo" atIndex: 1]; [myColors insertObject: @"Violet" atIndex: 3];

Objective-C Language • NSMutableArray

Deleting Elements

Remove at specific index: [myColors removeObjectAtIndex: 3]; Remove the first instance of a specific object: [myColors removeObject: @"Red"]; Remove all instances of a specific object: [myColors removeObjectIdenticalTo: @"Red"]; Remove all objects: [myColors removeAl...

Objective-C Language • NSMutableArray

Accessing elements

NSArray *myColors = @[@"Red", @"Green", @"Blue", @"Yellow"]; // Preceding is the preferred equivalent to [NSArray arrayWithObjects:...] Getting a single item The objectAtIndex: method provides a single object. The first object in an NSArray is index 0. Si...

Objective-C Language • NSArray

Spanning columns or rows

Table cells can span multiple columns or rows using the colspan and rowspan attributes. These attributes can be applied to <th> and <td> elements. <table> <tr> <td>row 1 col 1</td> <td>row 1 col 2</td> <td>row 1 c...

HTML • Tables

Element Language

The lang attribute is used to specify the language of element content and attribute text values: <p lang="en">The content of this element is in English.</p> <p lang="en" title="The value of this attribute is also in English.">The content of this el...

HTML • Content Languages

Elements with Multiple Languages

You can "overwrite" a language declaration: <p lang="en">This English sentence contains the German word <span lang="de">Hallo</span>.</p>

HTML • Content Languages

Handling Attributes with Different Languages

You can "overwrite" a parent element's language declaration by introducing any element apart from applet, base, basefont, br, frame, frameset, hr, iframe, meta, param, script (of HTML 4.0) with an own lang attribute: <p lang="en" title="An English paragraph"> ...

HTML • Content Languages

Base Document Language

It’s a good practice to declare the primary language of the document in the html element: <html lang="en"> If no other lang attribute is specified in the document, it means that everything (i.e., element content and attribute text values) is in that language. If the document con...

HTML • Content Languages

Section Element

The <section> element represents a generic section to thematically group content. Every section, typically, should be able to be identified with a heading element as a child of the section. You can use the <section> element within an <article> and vice-versa. Every section shou...

HTML • Sectioning Elements

Simple usage

Object initializers are handy when you need to create an object and set a couple of properties right away, but the available constructors are not sufficient. Say you have a class public class Book { public string Title { get; set; } public string Author { get; set; } // the rest o...

C# Language • Object initializers

Recurse the whole pattern

The construct (?R) is equivalent to (?0) (or \g<0>) - it lets you recurse the whole pattern: <(?>[^<>]+|(?R))+> This will match properly balanced angle brackets with any text in-between the brackets, like <a<b>c<d>e>.

Regular Expressions • Recursion

Relative group references

Subpatterns can be referenced with their relative group number: (?-1) will recurse into the previous group (?+1) will recurse into the next group Also usable with the \g<N> syntax.

Regular Expressions • Recursion

Using the Delegate Pattern (passing data back)

To pass data from the current view controller back to the previous view controller, you can use the delegate pattern. This example assumes that you have made a segue in the Interface Builder and that you set the segue identifier to showSecondViewController. The outlets and actions must also be ho...

iOS • Passing Data between View Controllers

Simple method annotation

Documentation comments are placed directly above the method or class they describe. They begin with three forward slashes ///, and allow meta information to be stored via XML. /// <summary> /// Bar method description /// </summary> public void Bar() { } Information in...

C# Language • XML Documentation Comments

Horizontal Rules

You can create a horizontal break to divide your text by placing three (or more) underscores ___ or asterisks *** or hyphens --- on their own line. You can create a horizontal break to divide your text by placing three (or more) underscores or asterisks or hyphens o...

Markdown • Text Formatting

Precompiled patterns

import re precompiled_pattern = re.compile(r"(\d+)") matches = precompiled_pattern.search("The answer is 41!") matches.group(1) # Out: 41 matches = precompiled_pattern.search("Or was it 42?") matches.group(1) # Out: 42 Compiling a pattern allows it to be r...

Python Language • Regular Expressions (Regex)