可以初始化/分配结构指针吗? [英] Possible to initialize/assign a struct pointer?

问题描述

假设我具有以下结构和两个版本来对其进行初始化:

Let's say I have the following struct and two versions to initialize it:

#include <stdio.h>

typedef struct Car *CarPtr;
typedef struct Car {
        const char*     name;
        unsigned int    price;
} Car;

int main(void) {

    Car ford = {
        .name = "Ford F-150",
        .price = 25000
    };
    print_struct(&ford);

    // is this possible to do in a single assignment?
    CarPtr jeep = {
        .name = "Jeep",
        .price = 40000
    };
    print_struct(jeep);

}

第二个版本可以直接使用吗?还是我需要按照以下方式做些事情:

Is the second version possible to do directly? Or do I need to do something along the lines of:

CarPtr jeep;
jeep->name = "Jeep";
jeep->price = 40000;

或者直接初始化 CarPtr 类型的正确方法是什么?

Or what's the proper way to initialize the CarPtr type directly?

推荐答案

除空指针外，指针需要指向存在的对象(可以是已分配但尚未填充的内存).您可以使用复合文字定义指针并将其初始化为同时创建的对象:

Pointers, other than null pointers, need to point to objects that exist (which can be memory that has been allocated but not yet filled in). You can define a pointer and initialize it to an object you create at the same time, using a compound literal:

CarPtr jeep = & (Car) { .name = "Jeep", .price = 40000 };

这是一种特殊的语法，括号中的类型名称与定义中的包含初始化程序的花括号相同.(不是演员.)

This is a special syntax, with the type name in parentheses followed by braces containing initializers just as in a definition. (It is not a cast.)

您还可以将复合文字或它的地址直接传递给函数:

You can also pass a compound literal or its address directly to a function:

print_struct(& (Car) { .name = "Jeep", .price = 40000 });

但是，这具有有限的用途，因为如果在函数内部完成此操作，则该对象是临时的.它的生存期仅在当前函数执行持续的时间内持续.您可以在函数外部使用复合文字，然后该文字才能持续执行所有程序.使用复合文字之前，您应该对复合文字的属性有一般的了解和认识.

However, this has limited uses, as, if this is done inside a function, the object is temporary; its lifetime lasts only as long as the current function execution lasts. You can use a compound literal outside a function, and then it lasts for all of program execution. You should have a general understanding and awareness of the properties of compound literals before using them.

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