zhifu ge - how to be weird in ruby - with notes
TRANSCRIPT
How To Be WeirdThe Idiomatic Ruby Ways
https://www.youtube.com/watch?v=5MgBikgcWnY
It takes 20 hours of deliberate practice to be reasonably good at something, anything.
The Algorithm of Rapid Ruby Acquisition
1. Learn enough to self-correct
2. Practice at least 20 hours
Practice at least 20 hourscodeeval.com
The second step is easy. There are numerous online resources for you to practice. One example of them is codeeval.com
Learn enough to self-correctlisten to this talk
The first step, however, is easier. You only have to listen to this talk. That’s recursion right there
Learn enough to self-correct
• Assignment
• Naming
• Control Expressions
• Methods
Assignment
Weirdness #1 Parallel Assignment
a = 'foo'b = 'bar'c = 'baz'd = 'foobar'
Instead of doing this:You can do:
a, b, c, d = 'foo', 'bar', 'baz', 'foobar'
this:but just because you can doesn’t mean you should: readability is bad
a = 'foo'b = 'bar'
a, b = b, a
good 1: swap variable assignment
def multi_return [1, 2]end
a, b = multi_return
good 2: multiple return values from a method
Naming
Weirdness #2 Method names can end with ?s
they return a boolean
examples• String#empty?
• String#include?
• String#start_with?
• String#end_with?
• Array#empty?
• Array#include?
• Range#include?
• Object#respond_to?
• Object#nil?
• Object#is_a?
Obejct#is_a? synonymous kind_of?/instance_of?
Control Expressions
Weirdness #3 everything has a Boolean value
Every expression in Ruby evaluates to an object, and every object has a Boolean value of either true or false? true and false are objects
if 0 puts “0 is true”else puts “0 is false”end
what is the output?
Only two objects has a false value, nil and false itself
Every expression in Ruby evaluates to an object, and every object has a Boolean value of either true or false? true and false are objects
Weirdness #4 if statements return a value
if(condition1) { result = x;} else if(condition2) { result = y;} else { result = z;}
In Java
if condition1: result = xelif condition2: result = yelse: result = z
In Python
In Ruby if statements return a value
The evaluation of the last executed statement.
result = if condition1 x elsif condition2 y else: z end
In Ruby
Exercise
what is the value of result?result = if true puts “hello” “hello” else “world” end
“hello”
what is the value of result?result = if false “hello” else “world” puts “world” end
nil
The evaluation of the last executed statement.
Weirdness #5 the unless keyword
if !condition do_somethingend
negative condition unless
unless condition do_somethingend
Observation: Ruby cares about readability
so much so that (Weirdness #6)
Ruby has modifier if/unless
so this is not good enough
if !condition do_somethingend
negative condition unless
unless condition do_somethingend
so this is not good enough
do_something if !condition
negative condition unless
do_something unless condition
this isQuestion: which one is better? Choose unless over if with negative condition
Weirdness #7 iterators
iterators help you iterate
how to do an infinite loop?
iterators help you iterate
while(true) { doSomething(); if(condition1) { break; }
if(condition2) { continue;}
}
In Java
while True: do_something() if condition1: break if condition2: continue
In Python
loop do do_something break if condition1 next if condition2end
In Ruby
loop is a method, not a keyword
loop do do_something break if condition1 next if condition2end
Kernel#loop repeatedly executes the block.We call this kind of ruby methods iterators. They take a block, and execute the block repeatedly.
how to do something a certain number of times?
iterators help you iterate
for(int i = 0; i < 10; i++) { doSomething();}
In Java
for i in range(10): do_something()
In Python
10.times do somethingend
In Ruby
10.times do |i| puts iend
5.upto(10) do |i| puts iend
10.downto(1) do |i| puts iend
Weirdness #8 iterators - Array and String
how to iterate an array?
iterators help you iterate
for(int i : a) { doSomething(i);}
In Java
for i in a: do_something(i)
In Python
a.each do |i| do_something(i)end
In Ruby
demoalso demo each_with_index
how to iterate a String?
iterators help you iterate
In Java
String s = “hello";
for(int i = 0; i < s.length(); i++) { System.out.println(s.charAt(i));}
In Python
s = “hello"
for c in s: print c
In Ruby
s = “hello"
s.each_char do |char| puts charend
demoalso demo: how to print index of each char
Methods
Weirdness #9 method calls
parenthesis are optional when calling methods
puts “hello” puts(“hello”)
Omit parentheses when:Omit parentheses around parameters for methods that are part of an internal DSL (e.g. Rake, Rails, RSpec), methods that have "keyword" status in Ruby (e.g. attr_reader, puts) and attribute access methods. Use parentheses around the arguments of all other method invocations.
omit parentheses when:
• there are no arguments
• the method is part of internal DSL
• the method has “keyword status”
attr_reader, puts, print
Omit parentheses when:Omit parentheses around parameters for methods that are part of an internal DSL (e.g. Rake, Rails, RSpec), methods that have "keyword" status in Ruby (e.g. attr_reader, puts) and attribute access methods. Use parentheses around the arguments of all other method invocations.
Weirdness #10 methods can take blocks
a lot of ruby methods take blocks
add 1 to every element in an array
In Java
int[] a = {1, 2, 3};
for(int i = 0; i < a.length; i++) { a[i]++;}
In Python
a = [1, 2, 3]
for i in range(len(a)): a[i] += 1
In Ruby
a = [1, 2, 3]
a = a.map { |i| i + 1 }
DemoArray#collect = Array#mapInvokes the given block once for each element of self.change every int to string
get the sum of all elements in an array
In Java
int[] a = {1, 2, 3};
int sum = 0;for(int i = 0; i < a.length; i++) { sum += a[i];}
In Python
a = [1, 2, 3]
sum = sum(a)
In Ruby
a = [1, 2, 3]
sum = a.inject { |a, e| a + e }
DemoEnumerable#reduce = Enumerable#injectshortcut: inject(:+)
Rails flavoured Minitest cases
class SomeControllerTest < ActionController::TestCase test “should do stuff” do assert_equal 2, 1 + 1 end def test_should_do_stuff assert_equal 2, 1 + 1 endend
Weirdness #11 implicit return in methods
a lot of ruby methods take blocks
the evaluated object of the last executed expression in a method is implicitly returned to the caller
Every expression in Ruby evaluates to an object,
def greet puts “hello” “hello”end
what is returned?
def greet “hello” puts “hello”end
def greet return “hello” puts “hello”end
References:
The Well-Grounded Rubyist by David A. Black
Ruby Style Guidehttps://github.com/bbatsov/ruby-style-guide
