做“指向非常量的常量指针”的正确方法在D？ [英] Right way to do "const pointer to non-const" in D?

问题描述

好，根据 http://dlang.org/const-faq.html# head-const 不能在D中具有指向非const的const指针。但是有一个好的实践：在const类中声明一个字段，如果您忘记初始化它，编译器会告诉您。有什么方法可以保护自己，避免忘记D中类的初始化指针字段？

Ok, according to http://dlang.org/const-faq.html#head-const there is no way to have a const pointer to non-const in D. But there is a good practice: declare a field in a class const and compiler let you know if you forget to initialize it. Is there any way to protect myself from forgetting to init pointer field of a class in D?

推荐答案

是：

void main() {
        // ConstPointerToNonConst!(int) a; // ./b.d(4): Error: variable b.main.a default construction is disabled for type ConstPointerToNonConst!int


        int b;
        auto a = ConstPointerToNonConst!(int)(&b); // works, it is initialized
        *a = 10;
        assert(b == 10); // can still write to it like a normal poiinter

        a = &b; // but can't rebind it; cannot implicitly convert expression (& b) of type int* to ConstPointerToNonConst!int


}

struct ConstPointerToNonConst(T) {
        // get it with a property without a setter so it is read only
        @property T* get() { return ptr; }
        alias get this;

        // disable default construction so the compiler forces initialization
        @disable this();

        // offer an easy way to initialize
        this(T* ptr) {
                this.ptr = ptr;
        }

        private T* ptr;
}

这篇关于做“指向非常量的常量指针”的正确方法在D？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！