Tutorial by Examples: er

Ordering directly on JSONField is not yet supported in Django. But it's possible via RawSQL using PostgreSQL functions for jsonb: from django.db.models.expressions import RawSQL RatebookDataEntry.objects.all().order_by(RawSQL("data->>%s", ("json_objects_key",))) This e...

Some examples for a window of size 3: ;; Naïve attempt: (loop for (first second third) on '(1 2 3 4 5) do (print (* first second third))) ;; prints 6 24 60 then Errors on (* 4 5 NIL) ;; We will try again and put our attempt into a function (defun loop-3-window1 (function list) (loop...

package com.example.xml.adapters; import javax.xml.bind.annotation.adapters.XmlAdapter; public class StringTrimAdapter extends XmlAdapter<String, String> { @Override public String unmarshal(String v) throws Exception { if (v == null) return null; ...

If the size of your content is fixed, you can use absolute positioning to 50% with margin that reduces half of your content's width and height: HTML <div class="center"> Center vertically and horizontally </div> CSS .center { position: absolute; background...

Microsoft Access has existed since 1992, and older versions continue to see regular use when business-critical database applications have been built on them. A very comprehensive resource summarizing the release history (with links to release notes, where available) is: Microsoft Access Version...

.my-div { width: 300px; height: 200px; background-size: 100%; background-repeat: no-repeat; background-image: linear-gradient(to right, black 0%,white 100%), url('https://static.pexels.com/photos/54624/strawberry-fruit-red-sweet-54624-medium.jpeg'); background-blend-mod...

A common thought pattern for inexperienced Java programmers is that exceptions are "a problem" or "a burden" and the best way to deal with this is catch them all1 as soon as possible. This leads to code like this: .... try { InputStream is = new FileInputStream(fileName);...

<dom-module id="using-listeners-obj"> <template> <style> :host{ width: 220px; height: 100px; border: 1px solid black; display: block; } #inner{ width: calc(100% - 10px); height: 50px; ...

Another way to add an event listener is to use on-event annotation in DOM. Below is an example using up event, which is fired when finger/mouse goes up <dom-module id="annotated-listener"> <template> <style> .inner{ width: calc(200px); he...

You can also add/remove listener imperatively using listen and unlisten method of Polymer <dom-module id="imparative-listener"> <template> <style> #inner{ width: 200px; height: 50px; border: 1px solid ...

Properties with notify:true also fires an event <link rel="import" href="../bower_components/paper-input/paper-input.html"> <dom-module id="property-change-event"> <template> <style></style> <paper-input id="input&quo...

An example of a class that contains a parcelable class inside: public class Repository implements Parcelable { private String name; private Owner owner; private boolean isPrivate; public Repository(String name, Owner owner, boolean isPrivate) { this.name = name; ...

Install webpack-dev-server via npm. npm i -D webpack-dev-server Configure webpack-dev-server by adding server.js. // server.js var webpack = require("webpack"); var WebpackDevServer = require("webpack-dev-server"); var config = require("./webpack.dev.config...

To create a package using a specific format, it is possible to pick the Generator to be used. Similar to CMake this may be done using the -G argument: cpack -G 7Z . Using this command line would package the built project in the current directory using the 7-Zip archive format. At the time of w...

You can define central config info's in a separate gradle include file Centralizing dependencies via "dependencies.gradle" file a stand alone properties file Versioning your builds via "version.properties" file or do it with root gradle.properties file the project structu...

build.gradle: dependencies { compile 'com.android.support:appcompat-v7:23.3.0' compile 'com.jakewharton.rxbinding:rxbinding-appcompat-v7:0.4.0' } menu/menu.xml: <menu xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.c...

Since the release of Gradle 2.2, the use of the android-apt plugin is no longer used. The following method of setting up Dagger 2 should be used. For older version of Gradle, use the previous method shown below. For Gradle >= 2.2 dependencies { // apt command comes from the android-apt plu...

First of all you need Uri and temp Folders and request codes : public final int REQUEST_SELECT_PICTURE = 0x01; public final int REQUEST_CODE_TAKE_PICTURE = 0x2; public static String TEMP_PHOTO_FILE_NAME ="photo_"; Uri mImageCaptureUri; File mFileTemp; Then init mFileTemp : public ...

Obfuscation is often considered as a magic solution for code protection, by making your code harder to understand if it ever gets de-compiled by hackers. But if you're thinking that removing the Log.x(..) actually removes the information the hackers need, you'll have a nasty surprise. Removing al...

X-Macros can be used for code generation, by writing repetitive code: iterate over a list to do some tasks, or to declare a set of constants, objects or functions. Here we use X-macros to declare an enum containing 4 commands and a map of their names as strings Then we can print the string values ...