Parsing Data using std::string

Saving Config Changes

How could we extend the `Config` class to allow writing the configuration back to a file, effectively saving changes made in-game?

Abstract art representing computer programming

To enable saving the configuration back to a file, we need to add a Save() method to our Config class.

This method will do the reverse of Load(): it will take the current values of the Config object's members and write them to a file in the correct format.

Implementing `Save()`

Here's how we can implement the Save() method:

1#include <SDL.h>
2#include <iostream>
3#include <string>
4#include <vector>
5
6class Config {
7 public:
8  std::string WindowTitle;
9  int WindowWidth;
10  int WindowHeight;
11  std::vector<int> Levels;
12
13  void Save(const std::string& Path) {
14    SDL_RWops* File{SDL_RWFromFile(
15      Path.c_str(), "w")};
16    if (!File) {
17      std::cout << "Failed to open config file "
18        "for writing: " << SDL_GetError() << "\n";
19      return;
20    }
21
22    std::string Content{""};
23    Content += "WINDOW_TITLE: "
24      + WindowTitle + "\n";
25    Content += "WINDOW_WIDTH: "
26      + std::to_string(WindowWidth) + "\n";
27    Content += "WINDOW_HEIGHT: "
28      + std::to_string(WindowHeight) + "\n";
29    Content += "LEVELS: ";
30    for (size_t i{0}; i < Levels.size(); ++i) {
31      Content += std::to_string(Levels[i]);
32      if (i < Levels.size() - 1) {
33        Content += ",";
34      }
35    }
36    Content += "\n";
37
38    SDL_RWwrite(
39      File,
40      Content.c_str(),
41      Content.size(),
42      1
43    );
44
45    SDL_RWclose(File);
46  }
47
117};
118
119int main() {
120  Config MyConfig;
121  MyConfig.WindowTitle = "My Awesome Game";
122  MyConfig.WindowWidth = 1024;
123  MyConfig.WindowHeight = 768;
124  MyConfig.Levels = {1, 2, 3, 4, 5};
125  MyConfig.Save("config.txt");
126}

1WINDOW_TITLE: My Awesome Game
2WINDOW_WIDTH: 1024
3WINDOW_HEIGHT: 768
4LEVELS: 1,2,3,4,5

Explanation

SDL_RWFromFile() for Writing: We use SDL_RWFromFile() with the "w" mode to open the file for writing. If the file doesn't exist, it will be created. If it does exist, it will be overwritten.
Building the Content String: We create a std::string called Content and build it up line by line, using + to append each key-value pair. We use std::to_string() to convert numeric values to strings.
SDL_RWwrite(): We use SDL_RWwrite() to write the entire Content string to the file.
SDL_RWclose(): We close the file using SDL_RWclose().

Usage Example

In your game, you might modify the Config object's properties during gameplay (e.g., the player changes settings in a menu).

Then, you can call Save("config.txt") to save the updated configuration to the file, making the changes persistent across game sessions.

This Question is from the Lesson:

Parsing Data using `std::string`

Learn how to read, parse, and use config files in your game using std::string and SDL_RWops

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8 hours ago

This Question is from the Lesson:

Parsing Data using `std::string`

Learn how to read, parse, and use config files in your game using std::string and SDL_RWops

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Saving Config Changes

How could we extend the `Config` class to allow writing the configuration back to a file, effectively saving changes made in-game?

Implementing `Save()`

Explanation

Usage Example

Parsing Data using `std::string`

Why do we use `Start = End + 1` to move to the next position after finding a delimiter (like `\n` or `,`)?

What if a key in our config file has multiple spaces before or after it, such as `" KEY : VALUE"`? How can we trim leading/trailing spaces from the key and value?

What changes would be needed to load the config from a different source, like a network stream, instead of a file?

How could we implement a default configuration that is used if the config file is missing or invalid?

When we encounter an error parsing a file, how can we output an error message that includes where the error occurred - for example, the line number within the file?

Parsing Data using `std::string`

Game Dev with SDL2

This course includes:

Professional C++

Saving Config Changes

How could we extend the Config class to allow writing the configuration back to a file, effectively saving changes made in-game?

Implementing Save()

Explanation

Usage Example

Parsing Data using std::string

Why do we use Start = End + 1 to move to the next position after finding a delimiter (like \n or ,)?

What if a key in our config file has multiple spaces before or after it, such as " KEY : VALUE"? How can we trim leading/trailing spaces from the key and value?

What changes would be needed to load the config from a different source, like a network stream, instead of a file?

How could we implement a default configuration that is used if the config file is missing or invalid?

When we encounter an error parsing a file, how can we output an error message that includes where the error occurred - for example, the line number within the file?

Parsing Data using std::string

Game Dev with SDL2

This course includes:

Professional C++

How could we extend the `Config` class to allow writing the configuration back to a file, effectively saving changes made in-game?

Implementing `Save()`

Parsing Data using `std::string`

Why do we use `Start = End + 1` to move to the next position after finding a delimiter (like `\n` or `,`)?

What if a key in our config file has multiple spaces before or after it, such as `" KEY : VALUE"`? How can we trim leading/trailing spaces from the key and value?

Parsing Data using `std::string`