BuildOptional and buildEither in Swift - Step-by-Step Execution

Concept Flow - BuildOptional and buildEither

Start

↓

Check Optional Value

Yes|No↓

buildOptional(value)

↓

Check Condition for Either

↓

buildEither(first:)

↓

Result Built

This flow shows how buildOptional handles optional values by including or skipping content, and buildEither chooses between two branches based on a condition.

Execution Sample

Swift

func test() {
  let opt: Int? = 5
  let result = buildOptional(opt) {
    "Value is \(opt!)"
  }
  let either = buildEither(first: "First")
  print(result ?? "No value", either)
}

This code uses buildOptional to include a string if the optional has a value, and buildEither to select the first branch.

Execution Table

Step	Action	Input	Result	Notes
1	Check optional 'opt'	opt = 5	Has value	Optional is not nil
2	Call buildOptional with value	5	"Value is 5"	Includes content inside optional
3	Call buildEither with first branch	first: "First"	"First"	Selects first branch
4	Print results	result = "Value is 5", either = "First"	Output: Value is 5 First	Prints both results
5	Change opt to nil	opt = nil	No value	Optional is nil, buildOptional returns nil
6	Call buildOptional with nil	nil	nil	No content included
7	Call buildEither with second branch	second: "Second"	"Second"	Selects second branch
8	Print results	result = nil, either = "Second"	Output: No value Second	Prints fallback and second branch

💡 Execution stops after printing results for both optional present and nil cases.

Variable Tracker

Variable	Start	After Step 1	After Step 5	Final
opt	5	5	nil	nil
result	nil	"Value is 5"	nil	nil
either	nil	"First"	"Second"	"Second"

Key Moments - 2 Insights

Why does buildOptional return nil when the optional is nil?

Because buildOptional only includes content if the optional has a value, as shown in execution_table row 6 where input is nil and result is nil.

How does buildEither decide which branch to take?

buildEither chooses the first or second branch explicitly, as shown in rows 3 and 7 where first or second branch is selected.

Visual Quiz - 3 Questions

Look at the execution_table at step 2, what is the result of buildOptional when opt = 5?

A nil

B "No value"

C "Value is 5"

D "First"

💡 Hint

Check the 'Result' column in execution_table row 2 for buildOptional with value.

At which step does buildOptional return nil because the optional is nil?

A Step 2

B Step 6

C Step 3

D Step 7

💡 Hint

Look at execution_table row 6 where input is nil and result is nil.

If we change buildEither to select the second branch at step 3, what would be printed?

A "Value is 5 Second"

B "Value is 5 First"

C "No value First"

D "No value Second"

💡 Hint

Refer to variable_tracker 'either' value changes and execution_table rows 3 and 7.

Concept Snapshot

buildOptional(value) includes content only if value is not nil.
buildEither(first:) or buildEither(second:) chooses one branch explicitly.
Use buildOptional to handle optional content.
Use buildEither to select between two alternatives.
If optional is nil, buildOptional returns nil.
buildEither does not depend on optional, chooses branch directly.

Full Transcript

This visual execution shows how Swift's buildOptional and buildEither work. buildOptional checks if an optional value exists. If it does, it includes the content; if not, it returns nil. buildEither chooses between two branches, first or second, explicitly. The execution table traces steps with optional present and nil cases, showing how results change. Variable tracking shows how opt, result, and either change over time. Key moments clarify why buildOptional returns nil when optional is nil and how buildEither selects branches. The quiz tests understanding of these steps and outcomes.