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demo5.cc
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demo5.cc
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// This is the original sample from Google's ECS library: Corgi.
// I just ported the sample to Kult just for comparisons.
// - rlyeh
// Copyright 2015 Google Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <string>
#include <stdio.h>
#include <ctime>
#include "kult.hpp"
// Data types
using WorldTime = float;
// This is the Component data structure for the CounterComponent. It holds an
// `int` counter for each Entity that will be incremented on calls to `update_counters`.
struct CounterData {
int counter;
template<class ostream> friend inline ostream& operator <<( ostream &os, const CounterData &self ) {
return os << "(counter=" << self.counter << ")", os;
}
};
// The second Component is called `ScreamingComponent`. It will be a simple Component
// that stores a `std::string` representing a string literal of an Entity's `battle_cry`.
struct ScreamingData {
std::string battle_cry;
template<class ostream> friend inline ostream& operator <<( ostream &os, const ScreamingData &self ) {
return os << "(battle_cry=" << self.battle_cry << ")", os;
}
};
// Components
kult::component<'cntr', CounterData> CounterComponent;
kult::component<'scre', ScreamingData> ScreamingComponent;
// Systems
kult::system<float> update_counters = [&]( WorldTime delta_time ) {
for( auto &entity : kult::join( CounterComponent ) ) {
entity[ CounterComponent ].counter++;
}
};
kult::system<float> update_entities = [&]( WorldTime delta_time ) {
if( delta_time > 10 ) {
for( auto &entity : kult::join( ScreamingComponent ) ) {
puts( entity[ ScreamingComponent ].battle_cry.c_str() );
}
}
};
int main() {
// Create all of the Entities.
kult::entity new_entity;
// Register an Entity with all the Components it should be associated with.
new_entity += CounterComponent;
new_entity += ScreamingComponent;
new_entity[ ScreamingComponent ].battle_cry = "ouch";
// Simulate a game-loop that executes 10 times with a random delta_time.
std::srand(static_cast<unsigned>(std::time(0)));
for (int x = 0; x < 10; x++) {
int mock_delta_time = std::rand() % 20 + 1; // Random delta_time from 1-20.
// You typically call EntityManager's `UpdateComponents` once per frame.
// In this sample, it will first execute CounterComponent's
// `update_counters` to increment the `counter` for each Entity registered
// with CounterComponent.
update_counters( mock_delta_time );
// Next, it will execute ScreamingComponent's `update_entities` to check
// if the `mock_delta_time` is greater than 10. If so, it will print out
// each Entity's `battle_cry` string for each Entity that is registered with
// ScreamingComponent.
update_entities( mock_delta_time );
}
// Output the Entity's `counter` data to show that it incremented correctly.
auto &entity_data = new_entity[ CounterComponent ];
printf("The current counter is = %d.\n", entity_data.counter);
// Inspect/serialization
printf("%s\n", new_entity.dump().c_str() );
}