Blocks and variable basics

Question 1

What is the purpose of a Variable?

Answer 1

to label and store data in memory.

This data can then be used throughout your program.

Question 2

What is the value of b at this point?
Why?

irb :001 > a = 4
=> 4
irb :002 > b = a
=> 4
irb :003 > a = 7
=> 7

Answer 2

b remains 4, while a was re-assigned to 7.

Variables point to values in memory, and are not deeply linked to each other.

Question 3

what does gets method stand for?

Answer 3

gets stands for “get string”

Question 4

what does variable’s scope determine?

Answer 4

where in a program a variable is available for use

Question 5

how is a variable’s scope defined?

Answer 5

defined by where the variable is initialized or created.

Question 6

In Ruby, variable scope is defined by a ___ ?

Answer 6

block.

Question 7

In Ruby, what is a block?

Answer 7

A block is a piece of code following a method invocation, usually delimited by either curly braces {} or do/end.

Be aware that not all do/end pairs imply a block*. The for…do/end is not a block, it is part of the Ruby language and not a method invocation.

Question 8

______ scope can access variables initialized in an _____ scope , but not vice versa.

Answer 8

Inner

outer

Question 9

When are blocks created?

Answer 9

A new block is created when we use each, times and other method invocations, followed by {} or do/end. And when using iterators such as loop and each.

Question 10

List examples of ruby blocks

Answer 10

.times…do/end, .each…do/end, loop…do/end

Question 11

List examples of things that are NOT ruby blocks

Answer 11

while, until, for…do/end, if…end, unless..end

Question 12

How do I identify a block?

Answer 12

If the {} or do/end immediately follows a method invocation (E.g. [object].[method]), it is considered a block (and thereby creates a new scope for variables). And an iterator such as loop, is a block. But while, until, and for…do/end code is part of the Ruby language and not a method invocation. Thus they are not blocks.

Question 13

How do blocks affect variable scope?

Answer 13

Variables created inside blocks are not accessible outside the block, because a new inner scope is created inside the block. But variables created inside code that is not a block, is accessable in outer scope, because a new inner scope was not created.

Question 14

Do blocks affect variables created in outer scope?

Answer 14

No. Variables created in outer scope, outside blocks or non blocks is ALWAYS accessable inside blocks and non blocks.

Inner scope can access variables initialized in an outer scope, but not vice versa.
So the outer scope cannot access variables initialized in an inner scope.