TIL, 2018-03-27. Redux Chapter at Last, Trying out Chef

Musings, Chef

• Wah I was not even using my free tier account! :(
• $ chef gem install knife-zero.
• rails-server-template problem
• Berkshelf: The dependency manager for Chef cookbooks.
• Cookbooks are the modules that tell chef how to install a piece of software.
• $ berks vendor ensures we have the correct cookbooks available in the folder berks-cookbooks. This path is specified in knife.rb.
• Unable to authenticate (Chef): Add authorized_keys.

local_mode true
chef_repo_path   File.expand_path('../' , __FILE__)
cookbook_path ["cookbooks", "berks-cookbooks"]

knife[:ssh_attribute] = "knife_zero.host"
knife[:use_sudo] = true
knife[:editor] = '/usr/local/bin/vim'
knife[:before_bootstrap] = "berks vendor"
knife[:before_converge]  = "berks vendor"

Musings, Ruby

• High Voltage layout has to be below the include.
• params[:action] to figure out what layout to render re: Bootstrap container lol.
• Sticky footer solved by flexbox
• Read up on gem configuration patterns-just put it in the lifelong-learning for now, when I need it.
• The hidden costs of inheritance
  • Inheritance-based modeling is most commonly used for behavior sharing, but what it actually provides is implementation sharing. The greater the inheritance tree is, the chance of clashing with a variable used by an ancestor grows.
  • The lack of true private methods in Ruby complicates the system further: there isn’t a way to write a method in a parent object that a child object can’t clash with or override.
  • Gigantic interface (a million methods, lol).
  • Balancing reuse and customization?
• AR tricks
  • Join with condition on the associated table: merge.
  • Subqueries: Post.where(user_id: User.created_last_month).
  • Booleans: Use User.where(tall: [false, nil]) because a .where.not will not catch the NULL case.
• The Well-Grounded Rubyist, Chapter 6
  • Ruby initializes variables if it sees it, even if it won’t get executed. ` if false; x = 1; end #=> x is nil, not unknown`
  • Capture match in conditional: if m = /la/.match(name)
  • case operator: when matches on ===.
  • Blocks have access to the variables that already exist when they’re created, but block variables (those between the pipes) are not the same as the ones outside.
  • Semicolon in the parameter list: Doesn’t overwrite variables outside.
  • Exceptions that get raised are instances of a class, not the actual Exception class itself.
  • Pros of creating your own exception class:
    • Inherit from StandardError to have a meaningful exception name and refine the semantics of the rescue operation.
    • Self-documenting.
    • Able to rescue this specific exception.
• The Well-Grounded Rubyist, Chapter 7
  • Literal constructors: String.new, Array.new (you can’t do Integer.new).
  • inspect is for overriding, independently of whether you override to_s (which is used when it’s string interpolated). inspect is for other programmers.
  • A display method exists, it logs stuff out (default to STDOUT).
  • Star operator: Unwraps its operand into components.
  • Conversion vs typecasting: Calling methods like to_s, to_i, and to_f results in a new object, not like in C where you use the object as a string or an integer.
    • In a sense, all objects are typecasting themselves constantly.
  • Role-playing method
    • to_str
    • to_ary
  • Some cool shit:
    • Empty class definition = false
    • Non-empty class definition = the same value as the last value they contain
    • Method definitions are false, even if what they return is a true value

Musings, React

• $ ./node_modules/.bin/babel-node app.js To execute JS, with babel-cli and babel-core in there? Lol.
• Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: object. You likely forgot to export your component from the file it's defined in.
  • WTF, I just powered on this part.
• Need to learn what export actually means. Reference
• JS Spread syntax (…) Reference
  • Can be used for concatenating arrays, constructing objects/hashes.
• To check if undefined in ES 2015+:
  • Just check varName === undefined or varName !== undefined.
• this.forceUpdate() to force a re-render.
  • forceUpdate is discouraged.

``` js // Pass argument to event handlers Reference

onChange = (name, e) => { // ES6 way of dynamic keys Reference this.setState({ [name]: e.target.value, }) };

<input onChange={(e) => this.onChange(‘name’, e)} value={this.state.name} type=’text’ />