Alternatives to Structured Binding for SDL_Color in Render()

In the lesson's Render() function, we used structured binding (a C++17 feature) to unpack the SDL_Color chosen by the conditional (ternary) operator:

1// Rectangle.h Render() excerpt - Structured Binding
2void Render(SDL_Surface* Surface) const {
3  auto [r, g, b, a]{ // Declares r, g, b, a 
4    isPointerHovering ? HoverColor : Color 
5  }; 
6
7  SDL_FillRect(
8    Surface, &Rect,
9    SDL_MapRGB(Surface->format, r, g, b)
10  );
11}

This declares four new variables (r, g, b, a) and initializes them directly from the corresponding members (.r, .g, .b, .a) of the SDL_Color object returned by the expression isPointerHovering ? HoverColor : Color. It's concise and directly extracts the needed components.

However, there are alternative ways to achieve the same result:

Alternative 1: Temporary SDL_Color Variable

You could first assign the result of the conditional operator to a temporary SDL_Color variable, and then access its members individually when calling SDL_MapRGB().

1// Rectangle.h Render() excerpt - Temporary Variable
2void Render(SDL_Surface* Surface) const {
3  // Choose the color first
4  SDL_Color currentColor{ 
5    isPointerHovering ? HoverColor : Color 
6  }; 
7
8  // Access members of the temporary variable
9  SDL_FillRect( 
10    Surface, &Rect, 
11    SDL_MapRGB( 
12      Surface->format, 
13      currentColor.r, 
14      currentColor.g, 
15      currentColor.b 
16    ) 
17  ); 
18}

• Pros: Very explicit steps, arguably easier for beginners to follow, compatible with older C++ versions (pre-C++17).
• Cons: Slightly more verbose than structured binding.

Alternative 2: Inline Conditional Operator (Less Recommended)

You could use the conditional operator directly inside the SDL_MapRGB() call for each color channel.

1// Rectangle.h Render() excerpt - Inline Conditional
2void Render(SDL_Surface* Surface) const {
3  SDL_FillRect(
4    Surface, &Rect,
5    SDL_MapRGB(
6      Surface->format,
7      // Choose R component
8      isPointerHovering ? HoverColor.r : Color.r, 
9      // Choose G component
10      isPointerHovering ? HoverColor.g : Color.g, 
11      // Choose B component
12      isPointerHovering ? HoverColor.b : Color.b  
13    )
14  );
15}

• Pros: Might seem compact initially.
• Cons: Much harder to read and maintain. The condition isPointerHovering is repeated three times, making the code verbose and prone to errors if the condition needs changing. This is generally considered poor practice.

Comparison

• Structured Binding: Offers a good balance of conciseness and readability for extracting multiple members from an object. Its main "drawback" here is that it requires C++17 and forces us to declare the a variable even though we don't use it in SDL_MapRGB().
• Temporary Variable: Clear and explicit, good fallback if C++17 isn't available or if the step-by-step logic is preferred.
• Inline Conditional: Generally avoided due to poor readability and repetition.

For this specific case, both structured binding and the temporary variable approach are reasonable choices. Structured binding is often favored in modern C++ for its elegance when unpacking objects or tuples.