Strings & Integers

Warmup

• In your own words:
  • What’s a string?
  • What’s an integer?
  • What’s a float?
• How/why do we use variables in Ruby?

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Strings

• Defined by quotations marks (single or double)
• Can be empty
• Like everything in Ruby, strings are objects

Which of the following are valid strings? Why?

• ’’
• “123”
• 123
• ”@*#%&”
• hello, world!
• ‘welcome to Turing’
• ‘987654321.”
• “hot chocolate is the best”

Substrings

• Access portions of a string using square brackets and indices

Single Characters

Type the following examples in IRB and determine what they do:

• “hello, world”[0]
• “Turing”[0]
• “ruby”[2]
• “lunch”[-1]

Ranges

Type the following examples in IRB and determine what they do:

• “hello, world”[0..4]
• “Turing”[0..1]
• “ruby”[1..-1]
• “lunch”[0..-2]

String Methods

• Structure
• Sample methods
  • #upcase
  • #capitalize
  • #center
• Can also call the following on any Ruby object
  • .methods
  • .class

Documentation Review

String Concatenation

• Can use + to concatenate strings
• If strings are saved to variables, can still use + to concatenate

String Interpolation

• Can use curly braces inside a double quoted string to perform string interpolation.

student = 'Carl'
"Welcome to class, " + student + "."
=> "Welcome to class, Carl."
"Welcome to class, #{student}"
=> "Welcome to class, Carl."

Variable Assignment

x = 10
=> 10
x
=> 10

Assigment and Evaluating Expressions

b = 10 + 5
=> 15
b
=> 15

What is c

c = 15
=> ?
c = "hello"
=> ?
c
=> ?

Naming Local Variables

• Requirements
  • always start with a lowercase letter (underscore is permitted, though uncommon)
  • have no spaces
  • do not contain most special characters like $, @, and &

Naming Local Variables

• Conventions
  • use snake case where each word in the name is lowercase and connected by underscores (_)
  • are named after the meaning of their contents, not the type of their contents
  • aren’t abbreviated

Naming Practice

Which of the following are invalid? Which go against convention?

• time_machine
• student_count_integer
• homeworkAssignment
• 3_sections
• top_ppl

Integers

123456789.class
1_000_000_000_000_000_000_000.class
5.6.class
1.239.class

Integer Practice

See lesson plan.

Documentation Review

Homework