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Make getter return value optional #12

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Merged
heavyrubberslave merged 3 commits into from
Feb 15, 2026
Merged

Make getter return value optional #12

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072cff9
Make getter return value optional
heavyrubberslave Feb 15, 2026
02abeaa
Fix outdated writeValue for BoolAttribute
heavyrubberslave Feb 15, 2026
176aff2
Add an optional example
heavyrubberslave Feb 15, 2026
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12 changes: 6 additions & 6 deletions examples/basic/src/main.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -13,20 +13,20 @@ static const char* mode = "off";

// --------- getters/setters (C function pointers) ----------
// Note: your attribute classes use function pointers: T(*)(void*), not lambdas.
static int32_t getSpeed(void*) { return speed; }
static std::optional<int32_t> getSpeed(void*) { return speed; }
static SlvCtrlParseError setSpeed(void*, int32_t v) { speed = v; return SlvCtrlParseError::Ok; }

static int32_t getMaxSpeed(void*) { return maxSpeed; }
static std::optional<int32_t> getMaxSpeed(void*) { return maxSpeed; }
static SlvCtrlParseError setMaxSpeed(void*, int32_t v) { maxSpeed = v; return SlvCtrlParseError::Ok; }

static int32_t getState(void*) { return state; }
static std::optional<int32_t> getState(void*) { return ready ? std::make_optional(state) : std::nullopt; }
static SlvCtrlParseError setState(void*, int32_t v) { state = v; return SlvCtrlParseError::Ok; }

static bool getReady(void*) { return ready; }
static std::optional<bool> getReady(void*) { return ready; }

static int32_t getBaud(void*) { return baud; }
static std::optional<int32_t> getBaud(void*) { return baud; }

static const char* getMode(void*) { return mode; }
static std::optional<const char*> getMode(void*) { return mode; }
static SlvCtrlParseError setMode(void*, const char* v) { mode = v; return SlvCtrlParseError::Ok; }

// --------- attributes ----------
Expand Down
29 changes: 15 additions & 14 deletions src/SlvCtrlProtocol.h
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Original file line number Diff line number Diff line change
@@ -1,8 +1,9 @@
#pragma once

#include <optional>
#include <type_traits>
#include <stdint.h>
#include <stddef.h>
#include <type_traits>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
Expand Down Expand Up @@ -79,7 +80,7 @@ struct IAttribute {
template <typename T>
class BaseAttribute : public IAttribute {
public:
using Getter = T (*)(void* ctx);
using Getter = std::optional<T> (*)(void* ctx);
using Setter = SlvCtrlParseError (*)(void* ctx, T value);

BaseAttribute(const char* name, Getter g, Setter s, void* ctx = nullptr) : name_(name), ctx_(ctx), getter_(g), setter_(s) {
Expand All @@ -97,8 +98,8 @@ class BaseAttribute : public IAttribute {
return SlvCtrlAccess::INVALID;
}

T getValue() const {
return getter_ ? getter_(ctx_) : T{};
std::optional<T> getValue() const {
return getter_ ? getter_(ctx_) : std::nullopt;
}

SlvCtrlParseError setValue(T value) {
Expand All @@ -107,7 +108,10 @@ class BaseAttribute : public IAttribute {
}

void writeValue(ISlvCtrlOut& out) const override {
out.write(this->getValue());
auto val = getValue();
if (val.has_value()) {
out.write(val.value());
}
}
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heavyrubberslave marked this conversation as resolved.

private:
Expand All @@ -120,7 +124,7 @@ class BaseAttribute : public IAttribute {
class IntAttribute : public BaseAttribute<int32_t> {
public:
IntAttribute(const char* name, Getter getter, Setter setter, void* ctx = nullptr)
: BaseAttribute<int32_t>(name, getter, setter, ctx) {}
: BaseAttribute<int32_t>(name, getter, setter, ctx) {}

SlvCtrlParseError setFromCString(const char* s) override {
if (!s) return SlvCtrlParseError::MissingValue;
Expand All @@ -140,7 +144,7 @@ class IntAttribute : public BaseAttribute<int32_t> {
class FloatAttribute : public BaseAttribute<float> {
public:
FloatAttribute(const char* name, Getter getter, Setter setter, void* ctx = nullptr)
: BaseAttribute<float>(name, getter, setter, ctx) {}
: BaseAttribute<float>(name, getter, setter, ctx) {}

SlvCtrlParseError setFromCString(const char* s) override {
if (!s) return SlvCtrlParseError::MissingValue;
Expand All @@ -159,7 +163,7 @@ class FloatAttribute : public BaseAttribute<float> {
class BoolAttribute : public BaseAttribute<bool> {
public:
BoolAttribute(const char* name, Getter getter, Setter setter, void* ctx = nullptr)
: BaseAttribute<bool>(name, getter, setter, ctx) {}
: BaseAttribute<bool>(name, getter, setter, ctx) {}

SlvCtrlParseError setFromCString(const char* s) override {
if (!s) return SlvCtrlParseError::MissingValue;
Expand All @@ -174,7 +178,9 @@ class BoolAttribute : public BaseAttribute<bool> {
}

void writeValue(ISlvCtrlOut& out) const override {
out.write(this->getValue() ? "true" : "false");
auto val = this->getValue();
if (!val.has_value()) return;
out.write(val.value() ? "true" : "false");
}
};

Expand Down Expand Up @@ -340,11 +346,6 @@ class StrAttribute : public BaseAttribute<const char*> {
out.write(slvCtrlAccessToString(access()));
out.write("[str]");
}

void writeValue(ISlvCtrlOut& out) const override {
const char* s = this->getValue();
out.write(s ? s : "");
}
};

// ---- Protocol ----
Expand Down