--011 /** 1.函数项类型 Fn Item Type 2.函数指针类型 Fn Pointer Type 3.闭包类型 Closure */ /**01*/ struct T(u8, u8); impl T { fn sum(a:u8, b:u8) -> u8 {a+b} fn math(&self) -> u8 { Self::sum(self.0, self.1) } } fn main() { let t = T(1,2); let add = T::sum; let add_math = T::math; assert_eq!(add(1,2), T::sum(1,2)); assert_eq!(add_math(&t), t.math()); } /**02*/ #![allow(unused)] type RGB = (u8, u8, u8); //别名 fn color(c: &str) -> RGB { (255, 255, 255) } fn show(c: fn(&str) -> RGB) { println!("{:?}", color("white")); } fn main() { let white = color; // Fn Item Type let w: fn(&str) -> RGB = white; show(white); //// fn(&str) -> RGB ， Fn Pointer Type show(w); //// 隐式转化 println!("{:?}", std::mem::size_of_val(&white)); // 0 ////零大小类型优化 println!("{:?}", std::mem::size_of_val(&w)); // 8 //// Fn, FnMut, FnOnce // let bibao = |s:&str| { (1, 1, 1) }; //定义闭包? show(bibao); } /**03*/ fn counter(i: i32) -> impl FnMut(i32) -> i32 { //i 环境变量，自由变量 move |n| n + i } fn main() { let mut f = counter(2); assert_eq!(3, f(1)); } --012 闭包 /** Ownership , &mut T , &T 所有权，可变借用，不可变借用 FnOnce<()> (to similar = fn(T) 函数指针) , FnMut<()> , Fn<()> call_once(()) , call_mut(()) , call(()) */ fn main() { let mut arr = [1, 2, 3]; let mut c = |i| { //// env_var for idx in 0..3 { arr[idx] = i; } println!("arr = {:?}", arr); }; c(6); } --013 /** 逃逸，非逃逸，实现了的Trait? */ fn c_mut() -> impl for<'a> FnOnce(&'a str) -> String { let mut s = "hello".to_string(); move |i| { s+= i; s } } fn foo<F: Fn() + Copy>(f: F) { f() } fn main() { let i = ", world"; let mut str_closure = c_mut(); let mut arr = [1,2,3]; let p = &mut arr; { let mut c = || { (*p)[0] = 0; }; c(); } let z = &p; //唯一不可变引用 }