在實現 Rust 結構時如何處理生命周期？

Question

所以，我一直在瀏覽 Handmade Hero 視頻系列，我認為將代碼翻譯成 Rust 會是一個有趣的練習。 但是，我以前從未真正處理過生命周期，現在我遇到了與它們相關的編譯錯誤。 我目前有以下代碼：

struct TextureData<'a> {
    texture: Texture<'a>,
    width: usize,
    height: usize,
    bytes_per_pixel: usize,
    pixels: Vec<u8>
}

impl TextureData<'_> {
    fn new(texture: Texture, width: usize, height: usize) -> Self {
        TextureData { texture, width, height, bytes_per_pixel: PIXEL_BYTES, pixels: Vec::new() }
    }

    fn fill_texture(&mut self) {
        let size = self.width * self.height * self.bytes_per_pixel;
        let mut pixels: Vec<u8> = Vec::with_capacity(size);
        for i in 0..(self.width * self.height){
            let x = i / self.width;
            let y = i % self.height;
            pixels.push((x % 0xff) as u8);
            pixels.push((y % 0xff) as u8);
            pixels.push(0);
            pixels.push(0);
        }

        self.pixels = pixels;
    }

    fn update(&mut self) {
        let pitch = self.width * self.bytes_per_pixel;
        self.texture.update(None, &self.pixels, pitch);
    }
}

我收到以下反饋：

error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'a` due to conflicting requirements
  --> src/main.rs:21:2
   |
21 |     TextureData { texture, width, height, bytes_per_pixel: PIXEL_BYTES, pixels: Vec::new() }
   |     ^^^^^^^^^^^
   |
note: first, the lifetime cannot outlive the anonymous lifetime #1 defined on the method body at 20:5...
  --> src/main.rs:20:5
   |
20 | /     fn new(texture: Texture, width: usize, height: usize) -> Self {
21 | |     TextureData { texture, width, height, bytes_per_pixel: PIXEL_BYTES, pixels: Vec::new() }
22 | |     }
   | |_____^
note: ...so that the expression is assignable
  --> src/main.rs:21:16
   |
21 |     TextureData { texture, width, height, bytes_per_pixel: PIXEL_BYTES, pixels: Vec::new() }
   |                   ^^^^^^^
   = note: expected  `sdl2::render::Texture<'_>`
              found  `sdl2::render::Texture<'_>`
note: but, the lifetime must be valid for the lifetime `'_` as defined on the impl at 19:18...
  --> src/main.rs:19:18
   |
19 | impl TextureData<'_> {
   |                  ^^
note: ...so that the expression is assignable
  --> src/main.rs:21:2
   |
21 |     TextureData { texture, width, height, bytes_per_pixel: PIXEL_BYTES, pixels: Vec::new() }
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   = note: expected  `TextureData<'_>`
              found  `TextureData<'_>`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0495`.

當然，我已經閱讀了 E0495 的文檔，但我不知道它在這種情況下如何應用。

Answer 1

您需要像聲明TextureData結構時那樣重復它：

impl<'a> TextureData<'a> {
    fn new(texture: Texture<'a>, width: usize, height: usize) -> Self {
        ...
    }

    ...
}

注意添加的 3 <'a> 。 它不一定是'a ，在這 3 個地方它同樣可以是'b 。

或者，如果你想使用“匿名生命周期”形式，那么你需要這樣寫。

impl TextureData<'_> {
    fn new(texture: Texture<'_>, width: usize, height: usize) -> TextureData<'_> {
        ...
    }

    ...
}