BuildBlock for combining results in Swift - Step-by-Step Execution

Concept Flow - BuildBlock for combining results

Start BuildBlock

↓

Evaluate each Result

↓

Check if all are success?

No→Return first failure

Yes↓

Combine success values

↓

Return combined success

The BuildBlock evaluates multiple Result values, returns the first failure if any, otherwise combines all successes.

Execution Sample

Swift

func combineResults() -> Result<(Int, Int, Int), String> {
    Result.buildBlock(
        .success(10),
        .success(20),
        .failure("Error")
    )
}

This code combines three Result values, returning the first failure or combined successes.

Execution Table

Step	Action	Result Evaluated	Outcome	Return Value
1	Evaluate first Result	success(10)	Success	Continue
2	Evaluate second Result	success(20)	Success	Continue
3	Evaluate third Result	failure("Error")	Failure found	Return failure("Error")
4	Stop evaluation	N/A	Failure returned	failure("Error")

💡 Third Result is failure, so BuildBlock returns failure immediately.

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
results	N/A	success(10)	[success(10), success(20)]	[success(10), success(20), failure("Error")]	failure("Error")

Key Moments - 2 Insights

Why does BuildBlock return failure immediately instead of combining all results?

Because BuildBlock stops at the first failure it finds, as shown in execution_table row 3, it returns failure("Error") without combining successes.

What happens if all Results are successes?

BuildBlock combines all success values into a tuple or combined value, as described in concept_flow and would return combined success.

Visual Quiz - 3 Questions

Look at the execution_table, what is the return value at step 3?

A success(20)

B failure("Error")

C success(10)

D combined successes

💡 Hint

Check execution_table row 3 where failure is found and returned.

At which step does BuildBlock stop evaluating further Results?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

See execution_table row 3 where failure is detected and evaluation stops.

If all Results were successes, what would BuildBlock return?

A The first success only

B A failure

C A combined success of all values

D An empty result

💡 Hint

Refer to concept_flow and key_moments about combining all successes.

Concept Snapshot

BuildBlock combines multiple Result values.
It returns the first failure found.
If all succeed, it combines success values.
Useful for aggregating multiple operations.
Stops early on failure to save work.

Full Transcript

This visual execution shows how Swift's BuildBlock combines multiple Result values. It evaluates each Result in order. If it finds a failure, it returns that failure immediately without checking others. If all are successes, it combines their values into one success. The execution table traces each step, showing evaluation and return values. The variable tracker shows how the list of results grows and ends with the failure. Key moments clarify why BuildBlock stops early and what happens if all succeed. The quiz tests understanding of these steps and outcomes.