Capítulo 1.5: Flujo de Control

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Introducción

Control flow determines the order in which your code executes. Enforce Script provides the familiar if/else, for, while, foreach, and switch constructs -- but with several important differences from C/C++ that will catch you off guard if you are not prepared. This chapter covers every control flow mechanism available, including the pitfalls unique to DayZ's scripting engine.

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if / else / else if

The if statement evaluates a boolean expression and executes a block of code when the result is true. You can chain conditions with else if and provide a fallback with else.

void CheckHealth(PlayerBase player)
{
    float health = player.GetHealth("", "Health");

    if (health > 75)
    {
        Print("Player is healthy");
    }
    else if (health > 25)
    {
        Print("Player is wounded");
    }
    else
    {
        Print("Player is critical");
    }
}

Null checks

In Enforce Script, object references evaluate to false when null. This is the standard way to guard against null access:

void ProcessItem(EntityAI item)
{
    if (!item)
        return;

    string name = item.GetType();
    Print("Processing: " + name);
}

Logical operators

Combine conditions with && (AND) and || (OR). Short-circuit evaluation applies: if the left side of && is false, the right side is never evaluated.

void CheckPlayerState(PlayerBase player)
{
    if (player && player.IsAlive())
    {
        // Safe -- player is checked for null before calling IsAlive()
        Print("Player is alive");
    }

    if (player.GetHealth("", "Blood") < 3000 || player.GetHealth("", "Health") < 25)
    {
        Print("Player is in danger");
    }
}

PITFALL: Variable redeclaration in else-if blocks

This is one of the most common Enforce Script errors. In most languages, variables declared inside one if branch are independent from variables in a sibling else branch. Not in Enforce Script. Declaring the same variable name in sibling if/else if/else blocks causes a multiple declaration error at compile time.

// WRONG -- Compile error!
void BadExample(Object obj)
{
    if (obj.IsKindOf("Car"))
    {
        Car vehicle = Car.Cast(obj);
        vehicle.GetSpeedometer();
    }
    else if (obj.IsKindOf("ItemBase"))
    {
        ItemBase item = ItemBase.Cast(obj);    // OK -- different name
        item.GetQuantity();
    }
    else
    {
        string msg = "Unknown object";         // First declaration of msg
        Print(msg);
    }
}

Wait -- that looks fine, right? The problem occurs when you use the same variable name in two branches:

// WRONG -- Compile error: multiple declaration of 'result'
void ProcessObject(Object obj)
{
    if (obj.IsKindOf("Car"))
    {
        string result = "It's a car";
        Print(result);
    }
    else
    {
        string result = "It's something else";  // ERROR! Same name as in the if block
        Print(result);
    }
}

The fix: Declare the variable before the if statement, or use unique names per branch.

// CORRECT -- Declare before the if
void ProcessObject(Object obj)
{
    string result;

    if (obj.IsKindOf("Car"))
    {
        result = "It's a car";
    }
    else
    {
        result = "It's something else";
    }

    Print(result);
}

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for Loop

The for loop is identical to C-style syntax: initializer, condition, and increment.

// Print numbers 0 through 9
void CountToTen()
{
    for (int i = 0; i < 10; i++)
    {
        Print(i);
    }
}

Iterating over an array with for

void ListInventory(PlayerBase player)
{
    array<EntityAI> items = new array<EntityAI>;
    player.GetInventory().EnumerateInventory(InventoryTraversalType.PREORDER, items);

    for (int i = 0; i < items.Count(); i++)
    {
        EntityAI item = items.Get(i);
        if (item)
        {
            Print(string.Format("[%1] %2", i, item.GetType()));
        }
    }
}

Nested for loops

// Spawn a grid of objects
void SpawnGrid(vector origin, int rows, int cols, float spacing)
{
    for (int r = 0; r < rows; r++)
    {
        for (int c = 0; c < cols; c++)
        {
            vector pos = origin;
            pos[0] = pos[0] + (c * spacing);
            pos[2] = pos[2] + (r * spacing);
            pos[1] = GetGame().SurfaceY(pos[0], pos[2]);

            GetGame().CreateObject("Barrel_Green", pos, false, false, true);
        }
    }
}

Nota: Do not redeclare the loop variable i if there is already a variable named i in the enclosing scope. Enforce Script treats this as a multiple declaration error, even in nested scopes.

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while Loop

The while loop repeats a block as long as its condition is true. The condition is evaluated before each iteration.

// Remove all dead zombies from a tracking list
void CleanupDeadZombies(array<DayZInfected> zombieList)
{
    int i = 0;
    while (i < zombieList.Count())
    {
        EntityAI eai;
        if (Class.CastTo(eai, zombieList.Get(i)) && !eai.IsAlive())
        {
            zombieList.RemoveOrdered(i);
            // Do NOT increment i -- the next element has shifted into this index
        }
        else
        {
            i++;
        }
    }
}

WARNING: There is NO do...while in Enforce Script

The do...while keyword does not exist. The compiler will reject it. If you need a loop that always executes at least once, use the flag pattern described below.

// WRONG -- This will NOT compile
do
{
    // body
}
while (someCondition);

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Simulating do...while with a Flag

The standard workaround is to use a bool flag that is true on the first iteration:

void SimulateDoWhile()
{
    bool first = true;
    int attempts = 0;
    vector spawnPos;

    while (first || !IsPositionSafe(spawnPos))
    {
        first = false;
        attempts++;
        spawnPos = GetRandomPosition();

        if (attempts > 100)
            break;
    }

    Print(string.Format("Found safe position after %1 attempts", attempts));
}

An alternative approach using break:

void AlternativeDoWhile()
{
    while (true)
    {
        // Body executes at least once
        DoSomething();

        // Check the exit condition at the END
        if (!ShouldContinue())
            break;
    }
}

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foreach

The foreach statement is the cleanest way to iterate over arrays, maps, and static arrays. It comes in two forms.

Simple foreach (value only)

void AnnounceItems(array<string> itemNames)
{
    foreach (string name : itemNames)
    {
        Print("Found item: " + name);
    }
}

foreach with index

When iterating over arrays, the first variable receives the index:

void ListPlayers(array<Man> players)
{
    foreach (int idx, Man player : players)
    {
        Print(string.Format("Player #%1: %2", idx, player.GetIdentity().GetName()));
    }
}

foreach over maps

For maps, the first variable receives the key and the second receives the value:

void PrintScoreboard(map<string, int> scores)
{
    foreach (string playerName, int score : scores)
    {
        Print(string.Format("%1: %2 kills", playerName, score));
    }
}

You can also iterate over maps with just the value:

void SumScores(map<string, int> scores)
{
    int total = 0;
    foreach (int score : scores)
    {
        total += score;
    }
    Print("Total kills: " + total);
}

foreach over static arrays

void PrintStaticArray()
{
    int numbers[] = {10, 20, 30, 40, 50};

    foreach (int value : numbers)
    {
        Print(value);
    }
}

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switch / case

The switch statement matches a value against a list of case labels. It works with int, string, enum values, and constants.

Important: NO fall-through

Unlike C/C++, Enforce Script switch/case does NOT fall through from one case to the next. Each case is independent. You can include break for clarity, but it is not required to prevent fall-through.

void HandleCommand(string command)
{
    switch (command)
    {
        case "heal":
            HealPlayer();
            break;

        case "kill":
            KillPlayer();
            break;

        case "teleport":
            TeleportPlayer();
            break;

        default:
            Print("Unknown command: " + command);
            break;
    }
}

switch with enums

enum EDifficulty
{
    EASY = 0,
    MEDIUM,
    HARD
};

void SetDifficulty(EDifficulty difficulty)
{
    float zombieMultiplier;

    switch (difficulty)
    {
        case EDifficulty.EASY:
            zombieMultiplier = 0.5;
            break;

        case EDifficulty.MEDIUM:
            zombieMultiplier = 1.0;
            break;

        case EDifficulty.HARD:
            zombieMultiplier = 2.0;
            break;

        default:
            zombieMultiplier = 1.0;
            break;
    }

    Print(string.Format("Zombie multiplier: %1", zombieMultiplier));
}

switch with integer constants

void DescribeWeaponSlot(int slotId)
{
    const int SLOT_SHOULDER = 0;
    const int SLOT_MELEE = 1;
    const int SLOT_PISTOL = 2;

    switch (slotId)
    {
        case SLOT_SHOULDER:
            Print("Primary weapon");
            break;

        case SLOT_MELEE:
            Print("Melee weapon");
            break;

        case SLOT_PISTOL:
            Print("Sidearm");
            break;

        default:
            Print("Unknown slot");
            break;
    }
}

Recuerda: Because there is no fall-through, you cannot stack cases to share a handler the way you would in C. Each case must have its own body.

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break and continue

break

break exits the innermost loop (or switch case) immediately.

// Find the first player within 100 meters
void FindNearbyPlayer(vector origin, array<Man> players)
{
    foreach (Man player : players)
    {
        float dist = vector.Distance(origin, player.GetPosition());
        if (dist < 100)
        {
            Print("Found nearby player: " + player.GetIdentity().GetName());
            break; // Stop searching
        }
    }
}

continue

continue skips the rest of the current iteration and jumps to the next one.

// Process only alive players
void HealAllPlayers(array<Man> players)
{
    foreach (Man man : players)
    {
        PlayerBase player;
        if (!Class.CastTo(player, man))
            continue; // Not a PlayerBase, skip

        if (!player.IsAlive())
            continue; // Dead, skip

        player.SetHealth("", "Health", 100);
        Print("Healed: " + player.GetIdentity().GetName());
    }
}

Nested loops with break

break only exits the innermost loop. To break out of nested loops, use a flag variable:

void FindItemInGrid(array<array<string>> grid, string target)
{
    bool found = false;

    for (int row = 0; row < grid.Count(); row++)
    {
        for (int col = 0; col < grid.Get(row).Count(); col++)
        {
            if (grid.Get(row).Get(col) == target)
            {
                Print(string.Format("Found '%1' at [%2, %3]", target, row, col));
                found = true;
                break; // Only exits inner loop
            }
        }

        if (found)
            break; // Exits outer loop
    }
}

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Thread Keyword

Enforce Script has a thread keyword for asynchronous execution:

// Declare a threaded function
thread void LongOperation()
{
    // This runs asynchronously
    Sleep(5000);  // Wait 5 seconds without blocking
    Print("Done!");
}

// Call it
thread LongOperation();  // Starts without blocking the caller

Importante: thread in Enforce Script is NOT the same as OS threads. It is more like a coroutine --- it runs on the same thread but can yield/sleep without blocking the game. Use CallLater instead of thread for most mod use cases --- it is simpler and more predictable.

Thread vs CallLater

Característica	thread	CallLater
Sintaxis	thread MyFunc();	GetGame().GetCallQueue(CALL_CATEGORY_GAMEPLAY).CallLater(this.MyFunc, delayMs, repeat);
Can sleep/yield	Yes (Sleep())	No (fires once or repeats at interval)
Cancellable	No built-in cancel	Yes (CallQueue.Remove())
Caso de uso	Sequential async logic with waits	Delayed or repeated callbacks

For most DayZ modding scenarios, CallLater with a timer is the preferred approach. Reserve thread for cases where you genuinely need sequential logic with intermediate waits (e.g., a multi-step animation sequence).

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Mejores Prácticas

• Use guard clauses (if (!x) return;) at the top of functions instead of deeply nested if blocks -- it keeps the happy path flat and readable.
• Declare shared variables before if/else blocks to avoid the sibling-scope redeclaration error unique to Enforce Script.
• Use foreach for simple iteration and for with index only when you need to remove elements or access neighbors.
• Replace do...while with while (first || condition) using a bool first = true flag -- this is the standard Enforce Script workaround.
• Prefer CallLater over thread for delayed or repeated actions -- it is cancellable, simpler, and more predictable.

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Observado en Mods Reales

Patrones confirmados estudiando código fuente de mods profesionales de DayZ.

Patrón	Mod	Detalle
Guard clause + continue in loops	COT / Expansion	Loops over players always continue on failed cast or !IsAlive() before doing work
switch on string commands	VPP Admin	Chat command handlers use switch(command) with string cases like "!heal", "!tp"
Flag variable to break nested loops	Expansion Market	Uses bool found = false with check after inner loop to exit outer loop
CallLater for delayed spawn	Dabs Framework	Prefers GetGame().GetCallQueue(CALL_CATEGORY_GAMEPLAY).CallLater() over thread

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Teoría vs Práctica

Concepto	Teoría	Realidad
do...while loop	Standard in most C-like languages	Does not exist in Enforce Script; causes a confusing compile error
switch fall-through	C/C++ cases fall through without break	Enforce Script cases are independent -- stacking cases does not share handlers
thread keyword	Sounds like multithreading	Actually a coroutine on the main thread; Sleep() yields, does not block
Variable scope in if/else	Sibling blocks should have independent scope	Enforce Script treats them as shared scope -- same variable name in both blocks is a compile error

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Errores Comunes

Error	Problema	Solución
Using do...while	Does not exist in Enforce Script	Use while with a bool first = true flag
Declaring same variable in if and else blocks	Multiple declaration error	Declare the variable before the if
Redeclaring loop variable i in nested scope	Multiple declaration error	Use different names (i, j, k) or declare outside
Expecting switch fall-through	Cases are independent, no fall-through	Each case needs its own complete handler
Modifying array while iterating with foreach	Undefined behavior, potential crash	Use index-based for loop when removing elements
Infinite while loop without break	Server freeze / client hang	Always ensure the condition will eventually be false, or use break

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Referencia Rápida

// if / else if / else
if (condition) { } else if (other) { } else { }

// for loop
for (int i = 0; i < count; i++) { }

// while loop
while (condition) { }

// Simulate do...while
bool first = true;
while (first || condition) { first = false; /* body */ }

// foreach (value only)
foreach (Type value : collection) { }

// foreach (index + value)
foreach (int i, Type value : array) { }

// foreach (key + value on map)
foreach (KeyType key, ValueType val : someMap) { }

// switch/case (no fall-through)
switch (value) { case X: /* ... */ break; default: break; }

// thread (coroutine-style async)
thread void MyFunc() { Sleep(1000); }
thread MyFunc();  // non-blocking call

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