Times method for counted repetition in Ruby - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the times method do in Ruby?

The times method runs a block of code a specific number of times, based on the integer it is called on.

beginner

How do you use times to print "Hello" 3 times?

You write 3.times { puts "Hello" }. This runs the puts "Hello" command 3 times.

intermediate

What value does the block variable in times represent?

The block variable represents the current count, starting from 0 up to one less than the number. For example, in 5.times { |i| puts i }, i goes from 0 to 4.

intermediate

What is the return value of the times method?

The times method returns the original integer it was called on. For example, 3.times { puts "Hi" } returns 3.

advanced

Can times be used without a block? What happens?

If times is called without a block, it returns an Enumerator. This lets you chain other methods or use it later.

What does 4.times { |i| puts i } print?

A 1 2 3

B 1 2 3 4

C 4 3 2 1

D 0 1 2 3

The block variable i starts at 0 and goes up to 3, so it prints 0, 1, 2, 3 each on a new line.

What is the return value of 5.times { puts "Hi" }?

A nil

B An array of 5 elements

C 5

D "Hi"

The times method returns the integer it was called on, which is 5.

What happens if you call 3.times without a block?

A It returns an Enumerator

B It raises an error

C It returns nil

D It prints 3 times

Without a block, times returns an Enumerator object.

Which of these is a correct way to repeat a task 2 times?

A 2.repeat { do_something }

B 2.times { do_something }

C times(2) { do_something }

D repeat(2) { do_something }

The correct Ruby method to repeat a block a number of times is times called on an integer.

In n.times { |i| ... }, what is the first value of i?

A 0

B 1

C n

D nil

The block variable i starts at 0 and increments by 1 each iteration.

Explain how the times method works in Ruby and give an example.

Think about how many times the code inside the block runs and what the block variable represents.

What happens if you call times without a block? How can this be useful?

Consider what Ruby returns when no block is given and how you might use that.

Practice

1. What does the Ruby times method do when called on an integer?

easy

A. Repeats the given block of code that many times starting from zero.

B. Returns an array with that many elements.

C. Creates a range from zero to the integer.

D. Prints the integer value to the screen.

Solution

1. Step 1: Understand the times method purpose

   The times method repeats a block of code a specified number of times, starting from zero.

2. Step 2: Identify what happens when called on an integer

   When called on an integer, it runs the block that many times, passing the current count (starting at zero) to the block.

3. Final Answer:

   Repeats the given block of code that many times starting from zero. -> Option A

4. Quick Check:

   5.times { |i| puts i } prints 0 to 4 [OK]

Hint: Remember: times runs code block count times from zero [OK]

Common Mistakes:

• Thinking it returns an array
• Assuming it starts counting from 1
• Confusing it with range creation

2. Which of the following is the correct syntax to print numbers 0 to 4 using times in Ruby?

easy

A. times(5) { |i| puts i }

B. 5.times do |i| puts i end

C. 5.times { i in puts i }

D. 5.times puts i

Solution

1. Step 1: Check Ruby times syntax

   The correct syntax is calling times on an integer with a block, either with do...end or curly braces.

2. Step 2: Identify the correct block parameter usage

   5.times do |i| puts i end uses 5.times do |i| puts i end, which is valid Ruby syntax to print 0 to 4.

3. Final Answer:

   5.times do |i| puts i end -> Option B

4. Quick Check:

   Correct block syntax = 5.times do |i| puts i end [OK]

Hint: Use integer.times do |i| ... end for correct syntax [OK]

Common Mistakes:

• Using times(5) which is invalid
• Incorrect block syntax like { i in ... }
• Omitting block braces or do/end

3. What will be the output of this Ruby code?

3.times { |i| puts i * 2 }

medium

A. 0
2
4

B. 1
2
3

C. 2
4
6

D. 0
1
2

Solution

1. Step 1: Understand the iteration count and block variable

   The 3.times runs the block 3 times with i values 0, 1, 2.

2. Step 2: Calculate the output for each iteration

   Each iteration prints i * 2: 0*2=0, 1*2=2, 2*2=4.

3. Final Answer:

   0 2 4 -> Option A

4. Quick Check:

   Multiply index by 2 = 0, 2, 4 [OK]

Hint: Multiply block index by 2 to get output [OK]

Common Mistakes:

• Assuming index starts at 1
• Printing index without multiplication
• Confusing output order

4. Identify the error in this Ruby code snippet:

5.times do i
  puts i
end

medium

A. puts cannot be used inside times block

B. times method cannot be used with do...end

C. Missing block parameter pipes | | around i

D. Integer 5 cannot call times method

Solution

1. Step 1: Check block parameter syntax

   In Ruby, block parameters must be enclosed in pipes: do |i| ... end.

2. Step 2: Identify the missing pipes causing syntax error

   The code uses do i without pipes, which is invalid syntax.

3. Final Answer:

   Missing block parameter pipes | | around i -> Option C

4. Quick Check:

   Block params need |i|, not just i [OK]

Hint: Always use |param| in block headers [OK]

Common Mistakes:

• Omitting pipes around block parameters
• Thinking do/end can't be used with times
• Misunderstanding times method usage

5. You want to create an array of squares of numbers from 0 to 4 using times. Which code correctly does this?

hard

A. squares = (0..4).times { |i| i * i }
puts squares

B. squares = 5.times { |i| i * i }
puts squares

C. squares = []
5.times do i
squares.push(i * i)
end
puts squares

D. squares = []
5.times { |i| squares << i * i }
puts squares

Solution

1. Step 1: Understand how to collect results in an array

   Since times returns the integer, not an array, we must create an empty array and push results inside the block.

2. Step 2: Check each option for correct syntax and logic

   squares = [] 5.times { |i| squares << i * i } puts squares initializes an empty array, uses 5.times with block parameter i, and appends i*i to the array correctly.

3. Final Answer:

   squares = [] 5.times { |i| squares << i * i } puts squares -> Option D

4. Quick Check:

   Use array and push inside times block [OK]

Hint: Create array first, then push inside times block [OK]

Common Mistakes:

• Assuming times returns an array
• Using invalid range with times
• Omitting block parameter pipes