Builtin type std::builtins::callable

Method implementations for callable objects (named functions, function pointers, closures)

Methods

• fn invoke<Args, Ret, F>(f: F, args: Args) -> Ret

  F: Fn(Args...) -> Ret

  source

  Call a function with arguments passed as a tuple.

  Example

  fn add(a: i32, b: i32) -> i32 {
      a + b
  }
  
  let args = (1, 2);
  let result = add.invoke(args);
  
  assert_eq!(result, 3);
  Run this example

• fn as_callback<Args, Ret, F>(f: &mut F) -> (&mut void, fn(&mut void, Args...) -> Ret)

  F: Closure + Fn(Args...) -> Ret

  source

  Converts a pointer to closure to a C-style state and function pointer pair.

  This function is used to pass closures to C functions that expect a function pointer and a state pointer, that is passed as the first argument to the function when the callback is called.

  Example

  use libc::{c_int, c_char};
  
  extern "C" fn sqlite3_exec(
      db: &mut sqlite3,
      sql: &c_char,
      callback: fn(&mut void, c_int, &mut &mut c_char, &mut &mut c_char) -> c_int,
      state: &mut void, // ⮥
      errmsg: &mut &mut c_char,
  ) -> libc::c_int;
  
  let db = /* ... */;
  let file = File::open(/* ... */);
  defer file.close();
  
  // Prints the rows of a table to a file that's captured by the closure.
  let print = |&file, num_cols: c_int, values: &mut &mut c_char, _: &mut &mut c_char| {
      /// ... print values to file ...
      0
  };
  
  let (state, callback) = print.as_callback();
  sqlite3_exec(
      &mut db,
      "SELECT * FROM users\0".as_ptr() as &c_char,
      callback,
      state,
      null
  );
  Run this example