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35 lines
858 B
35 lines
858 B
3 years ago
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## struct中的一个字段是另外一个字段的指针
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```rust
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#[derive(Debug)]
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struct Test {
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a: String,
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b: *const String,
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}
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impl Test {
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fn new(txt: &str) -> Self {
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Test {
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a: String::from(txt),
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b: std::ptr::null(),
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}
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}
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fn init(&mut self) {
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let self_ref: *const String = &self.a;
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self.b = self_ref;
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}
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fn a(&self) -> &str {
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&self.a
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}
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fn b(&self) -> &String {
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assert!(!self.b.is_null(), "Test::b called without Test::init being called first");
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unsafe { &*(self.b) }
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}
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}
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```
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Test provides methods to get a reference to the value of the fields a and b. Since b is a reference to a we store it as a pointer since the borrowing rules of Rust doesn't allow us to define this lifetime. We now have what we call a self-referential struct.
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