From 5ed2a60bec932e3cca4c6c4dd12e3a1e4077463e Mon Sep 17 00:00:00 2001
From: George Vasiliades <1221374+Poseidonas@users.noreply.github.com>
Date: Sun, 23 Aug 2026 13:13:37 +0300
Subject: [PATCH] fix(oop): assign the return value to the method name in
 Capacity

In ST a method returns by assigning to its own name. Capacity computes the
percentage into the protected _capacity member and stops there, so the
method returns 0 to its caller.

program.st reads that return value:

    capacity_percentage := tank.Capacity(currentVolume := current_volume);

and the exercise text asks for "Capacity : REAL that returns a real with
the percentage of capacity of the volume of the tank", so the exercise as
shipped does not do what it describes.

The member assignment is kept and the return added on top, which is the
shape GetState already uses in ValveBase.st:

    GetState := ValveState#Open;
    _state := GetState;

Reported in #38.
---
 .../exercises/4_inheritance_complex_valve/src/TankWithVolume.st  | 1 +
 06_oop_in_st/exercises/solution/src/TankWithVolume.st            | 1 +
 2 files changed, 2 insertions(+)

diff --git a/06_oop_in_st/exercises/4_inheritance_complex_valve/src/TankWithVolume.st b/06_oop_in_st/exercises/4_inheritance_complex_valve/src/TankWithVolume.st
index 69b53e7..5546e55 100644
--- a/06_oop_in_st/exercises/4_inheritance_complex_valve/src/TankWithVolume.st
+++ b/06_oop_in_st/exercises/4_inheritance_complex_valve/src/TankWithVolume.st
@@ -21,6 +21,7 @@ NAMESPACE FluidHandlingClass
                 currentVolume : REAL;
             END_VAR 
             _capacity := (currentVolume / volume) * 100;
+            Capacity := _capacity;
         END_METHOD
 
         METHOD PUBLIC OpenInlet 
diff --git a/06_oop_in_st/exercises/solution/src/TankWithVolume.st b/06_oop_in_st/exercises/solution/src/TankWithVolume.st
index eae50f3..1a5b9bb 100644
--- a/06_oop_in_st/exercises/solution/src/TankWithVolume.st
+++ b/06_oop_in_st/exercises/solution/src/TankWithVolume.st
@@ -19,6 +19,7 @@ NAMESPACE FluidHandlingInterfaces
                 currentVolume : REAL;
             END_VAR 
             _capacity := (currentVolume / volume) * 100;
+            Capacity := _capacity;
         END_METHOD
 
         METHOD PUBLIC OpenInlet