Tutorial by Examples: s

Error code 1215: Cannot add foreign key constraint

This error occurs when tables are not adequately structured to handle the speedy lookup verification of Foreign Key (FK) requirements that the developer is mandating. CREATE TABLE `gtType` ( `type` char(2) NOT NULL, `description` varchar(1000) NOT NULL, PRIMARY KEY (`type`) ) ENGINE=InnoD...

MySQL • Error codes

JSONObject.NULL

If you need to add a property with a null value, you should use the predefined static final JSONObject.NULL and not the standard Java null reference. JSONObject.NULL is a sentinel value used to explicitly define a property with an empty value. JSONObject obj = new JSONObject(); obj.put("some...

Java Language • JSON in Java

Using named pipes

Sometimes you may want to output something by one program and input it into another program, but can't use a standard pipe. ls -l | grep ".log" You could simply write to a temporary file: touch tempFile.txt ls -l > tempFile.txt grep ".log" < tempFile.txt This work...

Bash • Redirection

Context. Using a credential cache for elevated execution of code

While server side-code can run with elevated privileges, there is not an equivalent method to elevate privileges in client-side code (for obvious security reasons). As an alternative, you can specify credentials to emulate the access of a specific user or service account. To specify credentials, bu...

sharepoint • Working with Managed Client Side Object Model (CSOM)

Basics

Back references are used to match the same text previously matched by a capturing group. This both helps in reusing previous parts of your pattern and in ensuring two pieces of a string match. For example, if you are trying to verify that a string has a digit from zero to nine, a separator, such as...

Regular Expressions • Back reference

JSHint

JSHint is an open source tool which detects errors and potential problems in JavaScript code. To lint your JavaScript you have two options. Go to JSHint.com and paste your code in there on line text editor. Install JSHint in your IDE. Atom: linter-jshint (must have Linter plugin installed) ...

JavaScript • Linters - Ensuring code quality

ESLint / JSCS

ESLint is a code style linter and formatter for your style guide much like JSHint. ESLint merged with JSCS in April of 2016. ESLint does take more effort to set up than JSHint, but there are clear instructions on their website for getting started. A sample configuration for ESLint is as follows: {...

JavaScript • Linters - Ensuring code quality

JSLint

JSLint is the trunk from which JSHint branched. JSLint takes a much more opinionated stance on how to write JavaScript code, pushing you towards only using the parts Douglas Crockford deems to be its "good parts", and away from any code that Crockford believes to have a better solution. Th...

JavaScript • Linters - Ensuring code quality

Defining a new Struct

To define the struct called Person with an integer type variable age, integer type variable height and float type variable ageXHeight: struct Person { int age; int height; float ageXHeight; } Generally: struct structName { /+ values go here +/ }

D Language • Structs

Struct Constructors

In D we can use constructors to initialize structs just like a class. To define a construct for the struct declared in the previous example we can type: struct Person { this(int age, int height) { this.age = age; this.height = height; this.ageXHeight = cast(float)age...

D Language • Structs

Marshaling structs with private fields

As a good developer you have created following struct with both exported and unexported fields: type MyStruct struct { uuid string Name string } Example in Playground: https://play.golang.org/p/Zk94Il2ANZ Now you want to Marshal() this struct into valid JSON for storage in somet...

Go • JSON

Monad as a Subclass of Applicative

As of GHC 7.10, Applicative is a superclass of Monad (i.e., every type which is a Monad must also be an Applicative). All the methods of Applicative (pure, <*>) can be implemented in terms of methods of Monad (return, >>=). It is obvious that pure and return serve equivalent purposes, ...

Haskell Language • Monads

Width vs Viewport

When we are using "width" with media queries it is important to set the meta tag correctly. Basic meta tag looks like this and it needs to be put inside the <head> tag. <meta name="viewport" content="width=device-width,initial-scale=1"> Why this is impo...

CSS • Media Queries

Installation or Setup

NLTK requires Python versions 2.7 or 3.4+. These instructions consider python version - 3.5 Mac/Unix : Install NLTK: run sudo pip install -U nltk Install Numpy (optional): run sudo pip install -U numpy Test installation: run python then type import nltk NOTE : For older versions of P...

nltk • Getting started with nltk

Download file from FTP server

My.Computer.Network.DownloadFile("ftp://server.my/myfile.txt", "donwloaded_file.txt") This command download myfile.txt file from server named server.my and saves it as donwloaded_file.txt into working directory. You can specify absolute path for downloaded file.

Visual Basic .NET Language • FTP server

Download file from FTP server when login required

My.Computer.Network.DownloadFile("ftp://srv.my/myfile.txt", "donwload.txt", "Peter", "1234") This command download myfile.txt file from server named srv.my and saves it as donwload.txt into working directory. You can specify absolute path for downloaded fil...

Visual Basic .NET Language • FTP server

Upload file to FTP server

My.Computer.Network.UploadFile("example.txt", "ftp://server.my/server_example.txt") This command upload example.txt file from working directory (you could specify absolute path if you want) to server named server.my. File stored on the server will be named server_example.txt. ...

Visual Basic .NET Language • FTP server

Upload file to FTP server when login required

My.Computer.Network.UploadFile("doc.txt", "ftp://server.my/on_server.txt", "Peter", "1234") This command upload doc.txt file from working directory (you could specify absolute path if you want) to server named server.my. File stored on the server will be na...

Visual Basic .NET Language • FTP server

Getting binary representation of an image file

This example is inspired by this question. We'll assume you know how to load a file using the File API. // preliminary code to handle getting local file and finally printing to console // the results of our function ArrayBufferToBinary(). var file = // get handle to local file. var reader = new...

JavaScript • Binary Data

Single File Upload using multer

Remember to create folder for upload (uploads in example). install multer npm i -S multer server.js: var express = require("express"); var multer = require('multer'); var app = express(); var fs = require('fs'); app.get('/',function(req,res){ res.sendFil...

Node.js • File upload