To create a Rails application we use the rails global command which usesthe version of Rails installed via gem install rails. When inside thedirectory of your application, we use the bin/rails command which uses theversion of Rails bundled with the application.
Let's build a generator that creates an initializer file named initializer.rbinside config/initializers. The first step is to create a file atlib/generators/initializer_generator.rb with the following content:
Our new generator is quite simple: it inherits from Rails::Generators::Baseand has one method definition. When a generator is invoked, each public methodin the generator is executed sequentially in the order that it is defined. Ourmethod invokes create_file, which will create a file at the givendestination with the given content.
Rails is usually able to derive a good description if a generator is namespaced,such as ActiveRecord::Generators::ModelGenerator, but not in this case. We cansolve this problem in two ways. The first way to add a description is by callingdesc inside our generator:
First, notice that the generator inherits from Rails::Generators::NamedBaseinstead of Rails::Generators::Base. This means that our generator expects atleast one argument, which will be the name of the initializer and will beavailable to our code via name.
Also, notice that the generator has a class method called source_root.This method points to the location of our templates, if any. By default itpoints to the lib/generators/initializer/templates directory that was justcreated.
We see that copy_file created config/initializers/core_extensions.rbwith the contents of our template. (The file_name method used in thedestination path is inherited from Rails::Generators::NamedBase.)
When resolving a generator's name, Rails looks for the generator using multiplefile names. For example, when you run bin/rails generate initializer core_extensions,Rails tries to load each of the following files, in order, until one is found:
Rails will also look in multiple places when resolving generator template files.One of those places is the application's lib/templates/ directory. Thisbehavior allows us to override the templates used by Rails' built-in generators.For example, we could override the scaffold controller template or thescaffold view templates.
From the output, we can see that the scaffold generator invokes othergenerators, such as the scaffold_controller generator. And some of thosegenerators invoke other generators too. In particular, the scaffold_controllergenerator invokes several other generators, including the helper generator.
You may notice that the output for the built-in helper generatorincludes "invoke test_unit", whereas the output for my_helper does not.Although the helper generator does not generate tests by default, it doesprovide a hook to do so using hook_for. We can do the same by includinghook_for :test_framework, as: :helper in the MyHelperGenerator class. Seethe hook_for documentation for more information.
For example, let's say we want to override the test_unit:model generator withour own my_test_unit:model generator, but we don't want to replace all of theother test_unit:* generators such as test_unit:controller.
First, the template asks the user whether they would like to install Devise.If the user replies "yes" (or "y"), the template adds Devise to the Gemfile,and asks the user for the name of the Devise user model (defaulting to User).Later, after bundle install has been run, the template will run the Devisegenerators and rails db:migrate if a Devise model was specified. Finally, thetemplate will git add and git commit the entire app directory.
You may also find incomplete content or stuff that is not up to date. Please do add any missing documentation for main. Make sure to check Edge Guides first to verify if the issues are already fixed or not on the main branch. Check the Ruby on Rails Guides Guidelines for style and conventions.
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However, according to -US/docs/Web/JavaScript/Reference/Global_Objects/Array/map#Description, map will not call for unassigned element. This mean we need to initialise the new Array(n) before mapping. One standard technique is to use fill. The final result is the following.
We could use this generator in a for...of loop (which would be very efficient) or use an array spread to retrieve all values (note that this essentially builds the array which is essentially the same as the non-generator approaches.)
as satisfying as this is, you're exposing a third argument that anyone can override. In a modern tech stack, this code is hesitantly admissible only if you can guarantee that absolutely no one can set length to be anything but end - start, otherwise you need to invest in a much more complex testing framework, likely outweighing the expense of adding a second line to this function.
This is how I went about creating a different solution although it is only really beneficial by calling (value in target) and really only counts as a "typeof range" :) Just bored and playing around with proxies.
I am quite against writing all functions as arrow functions. The reason being that arrow functions are not bind-able and it refers to the this from the outer scope. I feel that it is designed to prevent us writing var self = this; and refer to self in a callback function. So I tend to write arrow functions only when it is a callback or when it is a one-off function. Also if we use arrow function instead of proper function declaration in this case, we will lose the advantage which function hoisting provides. This means range might not be accessible by some earlier parts of our code. But it is all down to personal preference, do tell me what you think.
I don't like ambiguity in code. When I'm reviewing code and have to stop and figure out what this is referring to, it makes me frown; with arrow functions I always know exactly what this is. The 'swap this and that' pattern in JS always struck me as a hack. One of the big wins of arrow functions is eliminating the this ambiguity.
I have a similar feeling for hoisting. I understand why it is part of the language, but it always feels like a path to ruin when I have to rely on some behind-the-scenes reshuffling by the interpreter to get my code to run.
All that said, you are correct that there are situations in which arrow functions are not appropriate, which also make me crazy. Having two ways to write functions just adds confusion. "We recommend using arrow functions everyhwere. Oh, sorry, was that a constructor? Write that one this way instead..."
On the other hand, I am a big fan of Haskell. And we tend to use _ to refer to variables which we don't use in the function. But I do agree with you that having meaningful names is a good practice and could help readability.
Even in Haskell, _ is a bad idea :) Think about the poor intern trying to learn the language while debugging your code. (And it isn't just Haskell...I did a lot of Perl back in the day, which at it best can look like line noise).
This is an Awesome string of code you've written. I'm partial to Python3 behavior of range though. Made a few minor adjustments yours. Better to steal like an artist then build from scratch.
Might be inefficient to create an array for large ranges, and only supports range of integers (no dates). Have you seen Ruby's Range class? ruby-doc.org/core-2.2.0/Range.html
You could still implement toArray() and offer a covers() function.
The for loop is by far the easiest to read and also by far the most efficient. Your last example was literally more than 15 times slower than the for loop. Far too many developers these days are trying to get all fancy when the simple solution is much better.
The story of the establishment of Canyonlands National Park is long and filled with controversy. First proposed in 1936, Escalante National Park would have covered much of the land surrounding the confluence of the Green and Colorado Rivers. Despite the efforts of such luminaries as Frederick Law Olmsted, Jr., Escalante National Park was never established. The movement to create it, however, set the stage for the later establishment of Canyonlands National Park.
Largely through the efforts of Bates Wilson, then Superintendent of Arches National Monument, and U.S. Senator Frank E. Moss of Utah, Canyonlands National Park was created and set aside by PL 88-590 on September 12, 1964. The story of this struggle is well told in the article "The Canyonlands National Park Controversy, 1961-64" by Thomas G. Smith, a copy of which is in Folder 510. The years immediately before and after the park's establishment were filled with controversy over whether the park's existence would be a boon to the tourist economy of southern Utah or a cursed loss of access to resources coveted by the extractive industries and ranchers of the area.
The shift from resource extraction towards tourism and resource protection dominated the park's management focus in the early years. Mining and minerals claims and grazing rights were problems faced by park management in the years immediately following establishment of the park. Later, as these situations were resolved, the park's resource managers turned their attention to the wildlife, notably the bighorn sheep. In addition, the development of roads and structures stimulated increased visitation. This, in turn, has brought about a need for more active planning in the management of the park and the visitors' experiences.
Management of the recreational use of the Colorado and Green Rivers was another concern. This involved concessions operations, special safety concerns during high water years, and policies regarding employees working on the river.
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