1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215
//! Have you ever needed to pass a mutable reference to yourself to a struct member? //! Now you can! 100% safe rust code. //! //! # Examples //! //! ## You can pass mutable references to self into member structs: //! //! ``` //! #[macro_use] //! extern crate detach; //! use detach::prelude::*; //! //! fn main() { //! struct Sub; //! impl Sub { //! pub fn write(&mut self, t: &mut Top) { //! t.0.push_str("test"); //! } //! } //! struct Top(pub String, pub Detach<Sub>); //! impl Top { //! pub fn run(&mut self) { //! detach_run!(self.1, |s| s.write(self)); //! } //! } //! let mut t = Top("".to_string(), Detach::new(Sub)); //! t.run(); //! assert_eq!("test", &t.0); //! } //! ``` //! //! ## You can invoke `detach_run!` with an exper: //! //! ``` //! #[macro_use] //! extern crate detach; //! use detach::prelude::*; //! //! fn main() { //! let mut i = Detach::new(42_i8); //! detach_run!(i, |z| z = 3); //! assert_eq!(3, *i); //! } //! ``` //! //! ## You can invoke `detach_run!` with a block: //! //! ``` //! #[macro_use] //! extern crate detach; //! use detach::prelude::*; //! //! fn main() { //! let mut i = Detach::new(42_i8); //! detach_run!(i, |z| { //! z = 3; //! }); //! assert_eq!(3, *i); //! } //! ``` //! //! ## You can return info from the macro: //! //! ``` //! #[macro_use] //! extern crate detach; //! use detach::prelude::*; //! //! fn main() { //! let mut i = Detach::new(42_i8); //! let z = detach_run!(i, |z| { //! z = 3; //! return z; //! }); //! assert_eq!(3, *i); //! assert_eq!(3, z); //! } //! ``` //! //! ## You cannot use ? directly (we wouldn't re-attach the member): //! //! ```compile_fail //! #[macro_use] //! extern crate detach; //! use detach::prelude::*; //! //! fn main() { //! let mut i = Detach::new(42_i8); //! detach_run!(i, |z| { //! z = 3; //! let r: Result<(), ()> = Ok(()); //! // THIS WON'T COMPILE: //! r?; //! }); //! assert_eq!(3, *i); //! } //! ``` //! //! ## But you can return results, and ? after the macro: //! //! ``` //! #[macro_use] //! extern crate detach; //! use detach::prelude::*; //! //! fn test() -> Result<(), ()> { //! let mut i = Detach::new(42_i8); //! detach_run!(i, |z| { //! z = 3; //! let r: Result<(), ()> = Ok(()); //! return r; //! })?; //! assert_eq!(3, *i); //! Ok(()) //! } //! //! fn main() { //! test().unwrap(); //! } //! ``` pub mod prelude { pub use crate::Detach; } #[macro_export] macro_rules! detach_run { ($item:expr, |$id:ident| $code:block) => {{ let mut $id = $item.take(); let out = (|| $code)(); $item.put($id); out }}; ($item:expr, |$id:ident| $code:expr) => {{ let mut $id = $item.take(); let out = (|| $code)(); $item.put($id); out }}; } /// Allows sub-struct to be easily detached and re-attached #[derive(Debug, Clone, Copy, Default, PartialEq, Eq, PartialOrd, Ord, Hash)] pub struct Detach<T>(Option<T>); impl<T> Detach<T> { /// create a new Detach instance pub fn new(inner: T) -> Self { Self(Some(inner)) } /// extract the owned inner instance pub fn to_inner(self) -> T { self.0.expect("detach exists-to_inner") } /// returns true if this instance contains `Some` value. pub fn is_attached(&self) -> bool { self.0.is_some() } /// take the owned inner instance (without droping the container) pub fn take(&mut self) -> T { std::mem::replace(&mut self.0, None).expect("detach exists-take") } /// replace the owned inner instance pub fn put(&mut self, t: T) { std::mem::replace(&mut self.0, Some(t)); } } impl<T> std::ops::Deref for Detach<T> { type Target = T; fn deref(&self) -> &Self::Target { self.0.as_ref().expect("detach exists-deref") } } impl<T> std::ops::DerefMut for Detach<T> { fn deref_mut(&mut self) -> &mut Self::Target { self.0.as_mut().expect("detach exists-deref-mut") } } impl<T> std::borrow::Borrow<T> for Detach<T> { fn borrow(&self) -> &T { self.0.as_ref().expect("detach exists-borrow") } } impl<T> std::borrow::BorrowMut<T> for Detach<T> { fn borrow_mut(&mut self) -> &mut T { self.0.as_mut().expect("detach exists-borrow-mut") } } impl<T> std::convert::AsRef<T> for Detach<T> { fn as_ref(&self) -> &T { self.0.as_ref().expect("detach exists-as-ref") } } impl<T> std::convert::AsMut<T> for Detach<T> { fn as_mut(&mut self) -> &mut T { self.0.as_mut().expect("detach exists-as-mut") } } impl<T> std::convert::From<T> for Detach<T> { fn from(t: T) -> Detach<T> { Self(Some(t)) } }