Tutorial by Examples: di

Misusing GROUP BY to return unpredictable results: Murphy's Law

SELECT item.item_id, uses.category, /* nonstandard */ COUNT(*) number_of_uses FROM item JOIN uses ON item.item_id, uses.item_id GROUP BY item.item_id will show the rows in a table called item, and show the count of related rows in a table called uses. It will also show the va...

MySQL • Error 1055: ONLY_FULL_GROUP_BY: something is not in GROUP BY clause ...

Displaying current angular2 version used in your project

To display current version, we can use VERSION from @angular/core package. import { Component, VERSION } from '@angular/core'; @Component({ selector: 'my-app', template: `<h1>Hello {{name}}</h1> <h2>Current Version: {{ver}}</h2> `, }) export class AppCompone...

Angular 2 • Commonly built-in directives and services

Nested if()...else VS if()..else Ladder

Nested if()...else statements take more execution time (they are slower) in comparison to an if()...else ladder because the nested if()...else statements check all the inner conditional statements once the outer conditional if() statement is satisfied, whereas the if()..else ladder will stop condit...

C Language • Selection Statements

Custom Camera Control - Mouse-based Sliding

Here's an example of a custom camera controller. This reads the position of the mouse within the client window, and then slides the camera around as if it were following the mouse on the window. index.html <html> <head> <title>Three.js Custom Mouse Camera Control Ex...

three.js • Camera Controls in Three.js

Discarding slow/outdated rest calls

A common usecase is to discard certain rest-calls, that are not needed any more after certain user-inputs. The most prominent example would be, when a user uses some search-function, makes a request, makes another request and for some reason the first request arrives after the second request and the...

rxjs • Common recipes

What is Grand central dispatch.

What is Concurrency? Doing multiple things at the same time. Taking advantage of number of cores available in multicore CPUs. Running multiple programs in parallel. Objectives of Concurrency Running program in background without hogging CPU. Define Tasks, Define Rules and let...

Objective-C Language • Grand Central Dispatch

Sending Downstream Messages using Postman

To do this in Postman, you simply have to set the following: Set request type to POST In the Headers, set the following: Content-Type = application/json Authorization = < Your FCM Server Key > (See your Firebase Console's Cloud Messaging Tab) Set the payload parameters in the Body...

firebase-cloud-messaging • Firebase Cloud Messaging

Binding function context

5.1 Every function has a bind method, which will create a wrapped function that will call it with the correct context. See here for more information. var monitor = { threshold: 5, check: function(value) { if (value > this.threshold) { this.display("Value is too high!&quot...

JavaScript • Context (this)

Creating Custom Error Messages in Model and in Controller

Let's say that you have the following class: public class PersonInfo { public int ID { get; set; } [Display(Name = "First Name")] [Required(ErrorMessage = "Please enter your first name!")] public string FirstName{ get; set; } [Display(Name = "L...

asp.net-mvc • Model validation

Customize the CSS (stylesheet) for a column by inserting a DIV element

'<div style="font-size:11pt">' || expression || '</div>'

netsuite • Exploiting formula columns in saved searches

Protect string formulas from corruption and injection attacks

In a string formula field, consider that some values might contain substrings which look to the browser like HTML. Unless this is intentional, it is important to protect the values from corruption. This is useful to avoid injection attacks: it prevents someone from entering HTML into a comment field...

netsuite • Exploiting formula columns in saved searches

Adding Custom Post Types to Main RSS Feed

Registering a custom post type does not mean it gets added to the main RSS feed automatically.You need to use request filter to add custom post types to main RSS feed. // Add 'books' custom post types on main RSS feed function add_book_post_types_to_rss($qv) { if (isset($qv['feed']) &&amp...

WordPress • Custom Post Types

Foreground Images

Basic foreground images can be inserted into an email document just like they are for web pages: <img src="http://www.yourserver.com/email/images/logo.png"> And they can be made links by wrapping them in an <a href> tag: <a href="http://www.yourwebsite.com"&gt...

email • Images

Adding profiling flags to CMake to use gprof

The series of events here is supposed to work as follows: Compile code with -pg option Link code with -pg option Run program Program generates gmon.out file Run gprof program To add profiling flags, you must add to your CMakeLists.txt: SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -pg&quot...

cmake • Variables and Properties

Bindings libraries may rename methods and interfaces

Not everything in a bindings library will have the same name in C# as it does in Java. In C#, interface names start with "I", but Java has no such convention. When you import a Java library, an interface named SomeInterface will become ISomeInterface. Similarly, Java doesn't have propert...

Xamarin.Android • Bindings

Directly filtering indices

For simple cases, you can filter data directly. a = np.random.normal(size=10) print(a) #[-1.19423121 1.10481873 0.26332982 -0.53300387 -0.04809928 1.77107775 # 1.16741359 0.17699948 -0.06342169 -1.74213078] b = a[a>0] print(b) #[ 1.10481873 0.26332982 1.77107775 1.16741359 0.176999...

numpy • Filtering data

Turn a sequence of indices into copies of an element

Expanding the parameter pack of indices in a comma expression with a value creates a copy of the value for each of the indices. Sadly, gcc and clang think the index has no effect and warn about it (gcc can be silenced by casting the index to void): #include <algorithm> #include <array>...

C++ • std::integer_sequence

Variable Cascading

CSS variables cascade in much the same way as other properties, and can be restated safely. You can define variables multiple times and only the definition with the highest specificity will apply to the element selected. Assuming this HTML: <a class="button">Button Green</a>...

CSS • Custom Properties (Variables)

Redirect with/without query params

Redirect without query params: RewriteRule ^route$ /new_route_without_query [L,R=301,QSD] Redirect with query params: RewriteCond %{QUERY_STRING} ^$ RewriteRule ^/?route$ %{REQUEST_URI}?query=param1&query2=param2 [NC,L,R=301]

Hypertext Access file • Rewriting and Redirecting

Download and install

OS X Download and run the OS X installer. Windows Download and run the Windows installer 32-bit 64-bit. Debian/Ubuntu Run the following to add our apt repository and install the CLI: $ sudo add-apt-repository "deb https://cli-assets.heroku.com/branches/stable/apt ./" $ curl -L https...

heroku • Command Line