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25 Cards in this Set
- Front
- Back
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def initialize
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class Language
def initialize(name, creator) @name = name @creator = creator end |
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interpolation
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#{@name}
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create instance of a class. Must pass parameters
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ruby = Language.new("Ruby", "Yukihiro Matsumoto")
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Call a method
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ruby.description
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Scope
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Variables and methods can be available everywhere (global), vars that are only available to certain methods (local variables), vars/methods that are members of a certain class, and ones that are only available to particular instances of a class (instance variables).
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Scope notation
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$ - global (if defined inside class, else no prefix needed), @-instance, @@-class
Can access global directly. Class need classname before '.' Instance needs object name before '.' |
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Key value syntax for hashes
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New: {hello: "Hello, world!"}
Old: {:hello=>"Hello, world!"} |
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Initialise var
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var =0
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Return var
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Just the name of the var, or return var
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Accessing a key in a hash
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puts my_hash["name"]
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Creating a hash
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Setting a variable equal to Hash.new creates a new, empty hash; it's the same as setting the variable equal to empty curly braces ({}).
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.each iterator
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friends.each { |x| puts "#{x}" }
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Accessing value of a hash - 4 methods
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stones.each { |k, v| puts "Key: #{k}, Value: #{v}" }
stones.each_key { |key| puts "#{key}" } stones.each_value { |val| puts "#{val}" } stones.each_pair { |k, v| puts "Key: #{k}, Value: #{v}" } |
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Class inheritance (of methods etc)
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class MyApp < Application
end |
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super method
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When you call super from inside a method, that tells Within method, just write 'super'
Looks in the superclass of the current class and find a method with the same name as the one from which super is called. If it finds it, Ruby will use the superclass' version of the method |
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attr_accessor syntax
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attr_accessor :y, :x
After def initialize block in class block |
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recursion
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If the user didn't choose q/Q above, thus calling the return "str" (ie exit), then we just the method again from within itself. This is called "recursion" and is a very useful way to loop through a program.
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Select method - what does it do?
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It takes a block and passes in each item one after the other. If the block returns true, then that item is included in the output; if it returns false, it is left out.
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PG gem connecting to database via hash, and closing connection
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@@conn = PG.connect(:dbname =>'shelter', :host => 'localhost')
@@conn.close |
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PG gem data insertion to database
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sqlclient = "insert into clients (name, age) values ('#{name}', '#{age}')"
@@conn.exec(sqlclient) |
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DSL
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domain specific language, eg rspec
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rspec DSL syntax
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describe "::new" do #label for test, can use any word
it "creates a new Bank object" do #msge for test |
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Creating instance variable within a Class
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Has to be in def initialize.
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When use rbenv rehash?
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Every time you install a new version of Ruby or install a gem that provides a command (write 'gem name' in CLI and press enter to check), run rbenv rehash to make sure any new commands are shimmed. When you execute a shim, rbenv determines which Ruby version to use
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Adding an instance to an array using a method
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def add_client(client)
@clients << client end #if use = then not adding to end of array - just var |
