如何在Rust中使用链接的方法调用编写惯用的构建模式？ [英] How to write an idiomatic build pattern with chained method calls in Rust?

问题描述

根据以下示例，可以在Rust中编写一个带有链式方法调用的构建模式，该方法可以按值或按引用传递（带有生命周期说明符）

Based on the following examples, its possible to write a build-pattern with chained method calls in Rust which either passes by value or by reference (with a lifetime specifier)

• 是否可以创建一个宏来实现构建器模式方法？


• 如何重载新方法？（最佳答案）


• https://github.com/rust-unofficial /patterns/blob/master/patterns/builder.md

• Is it possible to create a macro to implement builder pattern methods?
• How to overload the 'new' method? (top answer)
• https://github.com/rust-unofficial/patterns/blob/master/patterns/builder.md

Rust中的构建器模式可能看起来像这样：

A builder pattern in Rust may look something like this:

 ui::Button::new()
    .label("Test")
    .align(Align::Center)
    .build();

编写惯用的Rust时，有强烈的偏好吗？

When writing idiomatic Rust is there a strong preference for one over another?

在Rust中有一些很好的例子吗？

Is there some good example of how to write this in Rust?

推荐答案

实际上有两个取舍：

• 指定的二传手应该接受自己是按值还是引用？


• 最终的 build 方法是否应该接受 self 是按值还是参考？

• should the named setter accept self by value or reference?
• should the final build method accept self by value or reference?

我的建议是：

• 设置器的可变引用


• build 方法的值

• mutable reference for the setters
• value for the build method

这与 Rust Book中介绍的Builder Pattern ，该模型在 build 中使用了引用。

This differs slightly from the Builder Pattern presented in the Rust Book which uses a reference in build.

为什么通过可变参考传递二传手？

尽管编译器可以优化了对调用 fn label（self，& str）->所引起的移动。 ButtonBuilder ，它不能保证。

While a compiler may optimize away the moves caused by a call to fn label(self, &str) -> ButtonBuilder, it is not guaranteed.

另一方面，可变引用方式已经是最优的，因此您不必依赖优化器。

On the other hand, the mutable reference way is already optimal so that you need not rely on the optimizer.

为什么要按值传递最终的版本？

对于仅由 Copy 字段组成的构建器，<$ c之间没有区别$ c>构建接受自我或& self 。

For builders only composed of Copy fields, there is no difference between build taking self or &self.

但是，一旦构建器包含非 Copy 字段，就会传递& self 到 build 需要深度克隆这些字段。

However, as soon as the builder contains non-Copy fields, passing &self to build requires deep-cloning these fields.

另一方面，传递 self 按值允许 build 移动字段，避免不必要的复制。

On the other hand, passing self by value allows build to move the fields, which avoid unnecessary copies.

如果希望重复使用构建器，则构建器应实施 Clone 。

If one wishes to re-use the builder, then the builder should implement Clone.

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