从为const char *转换为字符串斯威夫特 [英] Converting from const char* to Swift string

问题描述

我有一个C函数，我从一个桥接报头，返回一个为const char *访问：

I have a c function which I access from a bridging header that returns a const char*:

const char* get_c_string();

我然后尝试将其转换为一个字符串斯威夫特：

I then try to convert it to a Swift String:

let str = String.fromCString(UnsafePointer<Int8>(get_c_string()))
print(str)

...但它只是打印垃圾：

... but it just prints garbage:

Optional("\u{14}\0\0")

我可以找到如何斯威夫特字符串传递给C，但不是周围的其他方式。我怎么能转换为const char * 来一个斯威夫特字符串？

I can find how to pass Swift string to C but not the other way around. How can I convert a const char* to a Swift String?

谢谢！

推荐答案

您斯威夫特code是正确的，可以将其缩短稍微

Your Swift code is correct, you can shorten it slightly to

// Swift 2:
let str = String.fromCString(get_c_string())
// Swift 3:
let str = String(cString: get_c_string())

但是，你必须确保指针从C函数返回
是当函数返回仍然有效。作为一个例子

However, you must ensure that the pointer returned from the C function is still valid when the function returns. As an example

const char* get_c_string() {
    char s[] = "abc";
    return s;
}

返回一个局部堆栈变量，这是不确定的行为的地址

returns the address of a local stack variable, which is undefined behavior.

您可能需要复制的字符串（然后再想的时候
并在释放内存）。

You might have to duplicate the string (and then think of when and where to release the memory).

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