Closures and variable binding in Ruby - Step-by-Step Execution

Concept Flow - Closures and variable binding

Define outer method

↓

Create inner closure (block/lambda)

↓

Inner closure captures outer variable

↓

Return or call closure

↓

Closure uses captured variable

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Variable binding shows closure remembers value

This flow shows how a closure captures variables from its surrounding method and remembers their values even after the method ends.

Execution Sample

Ruby

def make_counter
  count = 0
  -> { count += 1 }
end

counter = make_counter
puts counter.call
puts counter.call

This Ruby code defines a closure that remembers and updates a variable 'count' each time it is called.

Execution Table

Step	Action	Variable 'count'	Closure Created?	Output
1	Enter make_counter method	count = 0	No
2	Create lambda closure capturing 'count'	count = 0	Yes
3	Return closure from make_counter	count = 0	Yes
4	Call closure first time	count = 1	Yes	1
5	Call closure second time	count = 2	Yes	2

💡 Closure calls stop; 'count' variable is updated and remembered inside closure.

Variable Tracker

Variable	Start	After 1st call	After 2nd call	Final
count	0	1	2	2

Key Moments - 2 Insights

Why does the variable 'count' keep its value between calls to the closure?

Because the closure captures the variable 'count' from the outer method and remembers its state, as shown in execution_table rows 4 and 5 where 'count' increments and keeps its value.

Does the variable 'count' reset to 0 each time we call the closure?

No, it does not reset because the closure holds the binding to the original 'count' variable created in make_counter, so it updates the same variable instead of creating a new one (see execution_table rows 4 and 5).

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'count' after the first call to the closure?

A 1

B 0

C 2

D Undefined

💡 Hint

Check the 'Variable count' column at step 4 in the execution_table.

At which step is the closure created that captures the variable 'count'?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at the 'Closure Created?' column in the execution_table.

If we called the closure a third time, what would be the value of 'count'?

A 2

B 3

C 0

D Error

💡 Hint

See how 'count' increments by 1 each call in the variable_tracker.

Concept Snapshot

Closures capture variables from their surrounding method.
They remember and update these variables even after the method ends.
In Ruby, lambdas or blocks can act as closures.
Variable binding means the closure keeps the original variable, not a copy.
Each call to the closure can change the captured variable's value.

Full Transcript

This example shows how Ruby closures work by capturing a variable from an outer method. The method make_counter defines a variable 'count' starting at 0 and returns a lambda closure that increments 'count' by 1 each time it is called. The closure remembers the variable 'count' and its updated value between calls. The execution table traces each step: defining 'count', creating the closure, returning it, and calling it twice. The variable tracker shows how 'count' changes from 0 to 1, then 2. Key moments clarify that the closure holds the variable binding, so 'count' does not reset. The quiz tests understanding of when the closure is created, the value of 'count' after calls, and predicting future values. This helps beginners see how closures keep state in Ruby.