Category: DZone Python

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Let’s do some command line fun with Node.js :

1. Install colors: npm install -g colors 

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I assure you, this is a post about programming, it’ll just take a few paragraphs to get there.

There’s a biological mechanism known as resistance, and it plays out in many different systems. For example, as you habitually drink more alcohol, you gain a tolerance, which prevents you from getting drunk as easily. This can be called alcohol resistance. When you habitually run high levels of insulin, your body becomes less sensitive to insulin, making you insulin resistant. When you go into a loud room, your ears adjust down the sound, making you noise resistant. And when you change enough dirty diapers, you become smell resistant.

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I have an ASP.NET Core web application where I need to include a partial view only if it exists. The application uses areas and some areas may have their specific side menu. This blog post shows two ways to conditionally include a partial view in an ASP.NET Core layout page.

My goal is to do it the easiest way possible by using out-of-the-box things and making sure I don’t create an ugly looking mess. I wanted to avoid all kinds of additional classes to wrap dirty secrets away from controllers and views.

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This is a short post about how to implement INotifyPropertyChanged without using any advanced tooling. I have some small UWP applications where I’m using MVVM to separate presentation and logic. Here is how I use INotifyPropertyChanged with a base class for multiple view models.

First, one’s introduction to INotifyPropertyChanged comes usually through some existing view model. The interface is used to communicate to the view that some properties in the view model have changed. Take a look at thePropertyChanged event and theNotifyPropertyChanged method (this method is not part of the interface).

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Interfaces, those neat artifacts created to represent contracts to be fulfilled by classes. When appropriately used, they’re a very powerful way to express the expectations a client class has on implementations. Yet, most languages lack the tools to express those aspects that you can’t see by looking at the method signatures.

What should a method return under certain circumstances? If condition X is met, should it throw an exception? If so, of what type? All those questions can be answered by writing good documentation, that’s true, but, what about enforcing those rules? And who writes good docs in a world where working code is more important than documented code? That’s where the documenting facet of unit tests come in handy.

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For testing ONLYOFFICE document editors, we wrote a docx, xlsx, and pptx parser in Ruby. It is free and available both on GitHub and RubyGems.org via the AGPL v3 license.

In this article, we will tell you how it is done and how it works.

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Single Page Apps (SPA) have grown in popularity due to their ability to deliver dynamic user experiences, like those you would expect from a mobile or desktop application, quickly and easily. While SPAs are great from a user perspective, they can be a bit more challenging for your editors to make content changes and updates.

In Part 1 of this post, I showed you how to use a headless CMS and React to build a Single Page App. Today, I’ll show you how you can make your SPA content editable in a CMS.

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Hi there. I want to share with you how I implemented Google’s reCAPTCHA v3 in my Laravel app.

Securing HTML forms from bots is an essential part of the security of any web app these days. One common and easy solution to this is implementing a captcha system. And Google’s reCAPTCHA v3 makes it quite easy to both implement as a developer and use as a user (v3 users do not have to select images to verify).

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In the video below, we take a closer look at how to deploy a WAR file in a tomcat server manually Let’s get started!

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What Are Generators?

• Generators in ES6 are a new way of working with functions and iterators.
• They appear to be a function but behaves like an iterator which simplifies the task of writing iterators.
• They are different from a normal function, as they can stop mid-execution and then continue from where they stopped.
• In layman’s terms, they are similar to the way we put a marker/bookmark in a page of the book we are reading. Then later we resume reading the book from that particular page instead of starting all over again. Here we acted as a generator function.
• They can generate a series of results instead of a single value.

Generator Syntax

• Creating a generator is similar to a normal function, with the difference that it requires a * between the function keyword and function name.
• It allows any number of spaces or no spaces in between.
• It uses the yield keyword to pause and resume execution.
• Since it is just a function, we can use it anywhere just like we would with normal function, i.e. inside objects and class methods.
• Basic syntax:

// All below formats are valid with spaces/no spaces in between function keyword, * and function name.
function * functionName() {
    // Your generator related codes here.
}

// OR below format.
function *functionName() {
    // Your generator related codes here.
}

// OR below format.
function* functionName() {
    // Your generator related codes here.
}

// OR below format.
function  *  functionName() {
    // Your generator related codes here.
}

// OR below format.

function*functionName() {
    // Your generator related codes here.
}

// Inside Class method.
class testClass {
    *functionName() {}
}

// Inside object
var testObject = {
    *functionName() {}
}

Yield Keyword

• The yield keyword is used to return data and pause the execution of the generator.
• Every time the generator encounters yield, it halts the execution at that point and returns the specified value. It then resumes the execution upon calling the next() method on the Generator object until it finds the next yield.
• In the context of generators, we do not say that it returned a value. We say that it has yielded the value.
• Using return inside a generator will set the done property to true, after which it cannot generate any more values. All the code after the return statement will not execute.
• Syntax:

// Generator with yield. 
function * generator() {
    console.log('First execution.');
    yield 'Yield First execution, saved the state and exit';
    console.log('Second execution will be on next() call.');  
    yield 'Yield second execution, saved the state and exit';
}

const generatorObj = generator();

next() in Generators

• The generator returns an object on which we can call next().
• Every invocation of next() will return an object containing the returned value and the status of the generator’s execution.
• The value property will contain the value and the done property will return true or false for the generator’s execution status.
• When done becomes true, the generator stops and won’t generate any more values.

{
    value: Any,
    done: true|false
}

• Sample code (JSFiddle link:generator example): 

function * generator() {
    console.log('First execution.');
    yield 'Yield First execution, saved the state and exit';
    console.log('Second execution will be on next() call.');  
    yield 'Yield second execution, saved the state and exit';
}

const generatorObj = generator();

// After below execution, generator will yield value, return below object and pause execution.
// {value: 'Yield First execution, saved the state and exit', done: false}
setTimeout(() => console.log(generatorObj.next()), 1000);

// After below execution, generator will yield value, return below object and pause execution.
// {value: 'Yield First execution, saved the state and exit', done: false} 
setTimeout(() => console.log(generatorObj.next()), 3000);

// After below execution, generator will yield value, return below object and close execution.
// {value: undefined, done: true}
setTimeout(() => console.log(generatorObj.next()), 5000);

The below screenshot shows the different states of a generator during its execution of how it gets "suspended" when it encounters the yield keyword, resumes when next() is called, and then gets closed after the execution is complete:

If we use return then it will not execute any code present after the return statement. Sample code (JSFiddle link: generator with return statement):

function * generator() {
    console.log('First execution.');
    yield 'Yield First execution, saved the state and exit';
    return 'Execution ends here due to return and will not execute rest of the codes.';  
    // All below codes will not get executed.
    yield 'Yield second execution, saved the state and exit';
}

const generatorObj = generator();

// After below execution, generator will yield value, return below object and pause execution.
// {value: 'Yield First execution, saved the state and exit', done: false}
setTimeout(() => console.log(generatorObj.next()), 1000);

// After below execution, generator will yield value, return below object and completes the execution.
// {value: 'Execution ends here due to return and will not execute rest of the codes.', done: true}
setTimeout(() => console.log(generatorObj.next()), 3000);

// generator execution is already completed so it will just return value as undefined and done as true.
// {value: undefined, done: true}
setTimeout(() => console.log(generatorObj.next()), 5000);

We can also pass values to next().
Sample code (JSFiddle link: next() with value passed):

function * generator() {

    console.log('First execution.');

    yield 'Yield First execution, saved the state and exit';

    console.log('Second execution will be on next() call.');

    let passedArgument = yield 'Yield second execution, saved the state and exit';

    yield passedArgument;

}

const generatorObj = generator();
// After below execution, generator will yield value, return below object and pause