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Ruby Trivia 2
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Erik Berlin
November 05, 2015
Programming
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Ruby Trivia 2
Presented at the Berlin Ruby User Group (RUG::B) on November 5, 2015.
Erik Berlin
November 05, 2015
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Transcript
Ruby Trivia 2
What is the return value of Ruby’s method visibility keywords?
private, public, protected Question 1:
self Answer 1: Ruby’s method visibility keywords can be used
as r-values.
Given a button method that takes an argument and a
block, which of these are valid Ruby? button "string" { |n| n } button "string" do |n| n end button ["string"] { |n| n } button ["string"] do |n| n end Question 2:
All except: button("string") { |n| n } Answer 2:
How could this line be fixed? button("string") { |n| n
} Bonus Question:
How could this line be fixed? button("string") { |n| n
} Bonus Question: Answer: Add parentheses around the argument.
What is the result of this line: a Hash with
a String key, a Hash with a Symbol key, or a SyntaxError? {"key": "What happens?"} Question 3:
a Hash with a Symbol key* Answer 3: *In Ruby
2.2 and later. In earlier versions, it raises a SyntaxError.
What is the value of each argument? def foo(*w, a:
7, **t) puts "w: #{w}, a: #{a}, t: #{t}" end foo({a: 1, b: 2, "c" => 3, d: 4}) Question 4:
w: [{"c" => 3}] a: 1 t: {:b => 2,
:d => 4} Answer 4:
What happens if you add a positional argument to the
end? def foo(*w, a: 7, **t) puts "w: #{w}, a: #{a}, t: #{t}" end foo({a: 1, b: 2, "c" => 3, d: 4}, 5) Bonus Question:
What happens if you add a positional argument to the
end? w: [{:a=>1, :b=>2, "c"=>3, :d=>4}, 5] a: 7 t: {} Bonus Question:
When you inspect Object.new, Ruby outputs something like: #<Object: 0x00c1a551f1ab1e>
What are the properties and significance of this hex number? Question 5:
1. It’s the object’s address in memory. 2. It’s always
even. 3. It’s double the object’s object_id. Answer 5:
Answer 5:
Thanks for playing! Follow @sferik on Twitter for more Ruby
trivia and practica.