Tutorial by Examples: s

To let rails automatically and correctly link assets (css/js/images) in most cases you want to use built in helpers. (Official documentation) Image helpers image_path This returns the path to an image asset in app/assets/images. image_path("edit.png") # => /assets/edit.png image_...

A common pattern is to use an inline, or trailing, if or unless: puts "x is less than 5" if x < 5 This is known as a conditional modifier, and is a handy way of adding simple guard code and early returns: def save_to_file(data, filename) raise "no filename given" if fi...

preg_match checks whether a string matches the regular expression. $string = 'This is a string which contains numbers: 12345'; $isMatched = preg_match('%^[a-zA-Z]+: [0-9]+$%', $string); var_dump($isMatched); // bool(true) If you pass in a third parameter, it will be populated with the matchi...

NSString has a length property to get the number of characters. NSString *string = @"example"; NSUInteger length = string.length; // length equals 7 As in the Splitting Example, keep in mind that NSString uses UTF-16 to represent characters. The length is actually just the numbe...

This is the Python 2 syntax, note the commas , on the raise and except lines: Python 2.x2.3 try: raise IOError, "input/output error" except IOError, exc: print exc In Python 3, the , syntax is dropped and replaced by parenthesis and the as keyword: try: raise IOErro...

Rails uses sqlite3 as the default database, but you can generate a new rails application with a database of your choice. Just add the -d option followed by the name of the database. $ rails new MyApp -T -d postgresql This is a (non-exhaustive) list of available database options: mysql oracle...

"string".upcase # => "STRING" "STRING".downcase # => "string" "String".swapcase # => "sTRING" "string".capitalize # => "String" These four methods do not modify the original receiver. For exampl...

Suppose you have a repository structure like this: examples/ output.log src/ <files not shown> output.log README.md output.log in the examples directory is valid and required for the project to gather an understanding while the one beneath src/ is created while debugging a...

interface IFoo { } class Foo : IFoo { } class Bar : IFoo { } var item0 = new Foo(); var item1 = new Foo(); var item2 = new Bar(); var item3 = new Bar(); var collection = new IFoo[] { item0, item1, item2, item3 }; Using OfType var foos = collection.OfType<Foo>(); // result: IEnum...

Special care needs to be taken when there is a possibility that an array become an empty array when it comes to logical operators. It is often expected that if all(A) is true then any(A) must be true and if any(A) is false, all(A) must also be false. That is not the case in MATLAB with empty arrays....

To convert a String to uppercase, use uppercaseString: NSString *myString = @"Emphasize this"; NSLog(@"%@", [myString uppercaseString]; // @"EMPHASIZE THIS" To convert a String to lowercase, use lowercaseString: NSString *myString = @"NORMALIZE this"; N...

Strings are compared for equality using isEqualToString: The == operator just tests for object identity and does not compare the logical values of objects, so it can't be used: NSString *stringOne = @"example"; NSString *stringTwo = [stringOne mutableCopy]; BOOL objectsAreIdentical =...

Modules can have a special variable named __all__ to restrict what variables are imported when using from mymodule import *. Given the following module: # mymodule.py __all__ = ['imported_by_star'] imported_by_star = 42 not_imported_by_star = 21 Only imported_by_star is imported when usi...

The checked out file will overwrite not yet commited changes you did in this file. This command will check out the file file.example (which is located in the directory path/to/) and overwrite any changes you might have made to this file. git checkout some-branch path/to/file some-branch can be ...

To develop an application for iOS, you should start with an application called Xcode. There are other alternative tools you can use, but Xcode is Apple's official tool. Note, however, that it only runs on macOS. The latest official version is Xcode 8.3.3 with Xcode 9 (currently in beta) due to be re...

As of Tensorflow version 1.0 installation has become much easier to perform. At minimum to install TensorFlow one needs pip installed on their machine with a python version of at least 2.7 or 3.3+. pip install --upgrade tensorflow # for Python 2.7 pip3 install --upgrade tensorflow # for ...

There are two ways to connect to a MySQL/MariaDB server, depending on your infrastructure. Standard (TCP/IP) connection $dsn = 'mysql:dbname=demo;host=server;port=3306;charset=utf8'; $connection = new \PDO($dsn, $username, $password); // throw exceptions, when SQL error is caused $connection-...

Installing package manager Homebrew brew Paste that at a Terminal prompt. /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)" Installing Xcode IDE Download it using link below or find it on Mac App Store https://developer.apple.com/down...

Lists can be created in multiple ways. The recommended way is to use a List literal: var vegetables = ['broccoli', 'cabbage']; The List constructor can be used as well: var fruits = new List(); If you prefer stronger typing, you can also supply a type parameter in one of the following ways:...

Sets can be created via the constructor: var ingredients = new Set(); ingredients.addAll(['gold', 'titanium', 'xenon']);