我试图找到一种方法来解构方法的self参数。根据{{3}}：
在今天的会议上，我们有一个不同的计划，使自我论证变得无法构建。使用通用函数调用语法（UFCS＃11938），静态方法和实例方法之间不会有任何区别 - 它们都是相关的函数＆＃39;。此时，任何第一个参数的函数都是自我类型，可以使用方法语法调用，而
self，&self和&mut self只是{{1}的糖通过不使用自糖，可以正常地对self参数进行解构。
我编写了以下代码，但它没有像我预期的那样工作，因为所有三个打印函数都可以用作方法。
self: &Self struct Vector {
x: i32,
y: i32,
z: i32,
}
impl Vector {
fn print1(self: &Self) {
println!("{} {} {}", self.x, self.y, self.z);
}
// destructure self argument
fn print2(&Vector{x, y, z}: &Self) {
println!("{} {} {}", x, y, z);
}
// use another name for the first argument
fn print3(this: &Self) {
println!("{} {} {}", this.x, this.y, this.z);
}
}
fn main() {
let v = Vector{x: 1, y: 2, z: 3};
Vector::print1(&v); // work
v.print1(); // work
Vector::print2(&v); // work
v.print2(); // not work
Vector::print3(&v); // work
v.print3(); // not work
}
仅用于测试是否可以使用print3()以外的名称作为方法的第一个参数。
它给出了这个编译错误：
self似乎error: no method named `print2` found for type `Vector` in the current scope
--> 1.rs:27:7
|
27 | v.print2(); // not work
| ^^^^^^
|
= note: found the following associated functions; to be used as methods, functions must have a `self` parameter
note: candidate #1 is defined in an impl for the type `Vector`
--> 1.rs:12:5
|
12 | fn print2(&Vector{x, y, z}: &Self) {
| _____^ starting here...
13 | | println!("{} {} {}", x, y, z);
14 | | }
| |_____^ ...ending here
error: no method named `print3` found for type `Vector` in the current scope
--> 1.rs:29:7
|
29 | v.print3(); // not work
| ^^^^^^
|
= note: found the following associated functions; to be used as methods, functions must have a `self` parameter
note: candidate #1 is defined in an impl for the type `Vector`
--> 1.rs:16:5
|
16 | fn print3(this: &Self) {
| _____^ starting here...
17 | | println!("{} {} {}", this.x, this.y, this.z);
18 | | }
| |_____^ ...ending here
和print2()未被识别为print3()的方法。
Vector参数？self只是糖。这是否意味着self以外的名称可用于方法的第一个参数？答案 0 :(得分：9)
这最初是为了通过通用函数调用实现的，但是向后兼容，因为这意味着var ItemViewModel1 = function (data) {
var self = this;
self.PAR1 = ko.observable(data.PAR1)
self.PAR2 = ko.observable(data.PAR2)
self.PAR3 = ko.observable(data.PAR3)
self.PAR4 = ko.observable(data.PAR4)
// … etc
}
var MasterViewModel1 = function (data) {
var self = this;
ReportBaseViewModel.call(self)
}
var ReportBaseViewModel = function () {
var self = this;
/* commonly used vars */
self.report = ko.observable();
self.searchedCallBackFunction = ko.observable();
self.items = ko.observableArray();
self.selecteditem = ko.observable();
self.selectedPerson = ko.observable();
/* method: print */
self.PrintEventHandler = function (data) { window.print(); };
/* method: add items to array */
self.AddItems = function (data) {
var newitems = ko.utils.arrayMap(data, function (item) {
c = new window[self.itemname](item);
return c;
});
self.items(newitems);
};
/* eventhandler: select one item */
self.SelectEventHandler = function (item) {
selecteditem(item);
};
self.GetReport = function (selectedPerson, viewContainer, url, itemName) {
self.selectedPerson(selectedPerson);
self.itemname = itemName;
var jqxhr = $.ajax({
url: url,
type: "GET"
}).done(function (data, textStatus, jqXHR) {
if (data != null) {
self.AddItems(data);
$('#' + viewContainer).show();
document.getElementById(viewContainer).scrollIntoView();
}
}).fail(function (jqXHR, textStatus, errorThrown) {
console.log('fail' + JSON.stringify(jqXHR));
toastr.options = {
"closeButton": true,
"debug": false,
"newestOnTop": false,
"progressBar": false,
"positionClass": "toast-top-right",
"preventDuplicates": false,
"onclick": null,
"showDuration": "0",
"hideDuration": "1000",
"timeOut": "0",
"extendedTimeOut": "0",
"showEasing": "swing",
"hideEasing": "linear",
"showMethod": "fadeIn",
"hideMethod": "fadeOut"
};
toastr["error"]("ERROR");
}).always(function (jqXHR, textStatus, errorString) {
if (typeof self.searchedCallBackFunction() === 'function') {
self.searchedCallBackFunction();
}
});
}
}
突然等同于fn foo(bar: &Self)，这可能会因新的问题而中断方法调用方法突然出现。
您可以在函数体中使用fn foo(self: &Self)绑定对显式self参数进行解构：
let答案 1 :(得分：0)
impl Vector {
fn print(&self) {
// destructure self argument
let Vector { x, y, z } = &self;
println!("{} {} {}", x, y, z);
}
}