[英]Runtime Error in using function call by reference?
I have a class defined as, 我有一个定义为
class dimension{
public:
dimension();
const char* getname();
long ing getlength();
void setname(const char* text)
void setlength(long int size)
virtual ~dimension();
private:
const char* name;
long int length;
}
I am getting error regarding the functions setname
and setlength
are of importance so their definitions are as, 我在函数
setname
和setlength
的重要性方面遇到错误,因此它们的定义如下:
void dimension::setname(const char* text)
{
dimension::name = text;
}
void dimension::setlength(long int size)
{
dimension::length = size;
}
Now i have 2 functions which i am using to read an array of objects of class dimension from a file. 现在,我有2个函数,可用于从文件中读取类维的对象数组。 Their definition is as.
他们的定义是。
void read_dimension(dimension** dims, int*ndims, const char* text, long int size)
{
int i;
*dims = new dimension[*ndims];
for(i=0; i<ndims; i++)
{
(*dims)[i].setname(text)
(*dims)[i].setlength(size)
}
}
void read_file(char *path, dimension** dims, int *ndims)
{
//do-- open file and read the variables ndims, text and size from it.
read_dimension(dims, ndims, text, size);
//do-- print name and length of all elements of (*dims).
}
Now, i am calling these functions in main as 现在,我主要将这些功能称为
int main()
{
//do-- get file path
dimesnion* gdims;
int num_dims;
read_file(path, &gdims, &num_dims);
//do-- print name and length of each element of gdims.
return 0;
}
When i run the code the variable "name"
printed from the the functions read_dimension()
and main()
are different but the variable "length"
is the same. 当我运行代码时,从函数
read_dimension()
和main()
打印的变量"name"
不同,但变量"length"
相同。
I can't figure out why this is happening. 我不知道为什么会这样。
I would be glad if anyone could help. 如果有人可以帮助我,我会很高兴。
There's no doubts text is a local variable in read_dimension function, probably an array of char. 毫无疑问,文本是read_dimension函数中的局部变量,可能是char数组。 dimension::setname assigns one pointer to another, as already mentioned, what happens when text variable in read_dimension function goes out of scope?
如上所述,Dimension :: SetName将一个指针分配给另一个指针,当read_dimension函数中的文本变量超出范围时会发生什么? It'll die... Now your pointer in dimension class points to "nowhere".
它会死...现在您在维度类中的指针指向“无处”。 I prefer to use const char * as string literals or as pointer to some char in array of chars.
我更喜欢使用const char *作为字符串文字或作为char数组中某些char的指针。 If you want to store a string you'd copy it via strcpy maybe, of course destination array of char with sufficient space must exists.
如果要存储字符串,则可以通过strcpy复制它,当然,必须存在具有足够空间的char目标数组。
What's the purpose of this code: dimension::name = text; 这段代码的目的是什么:Dimensions :: name = text; and dimension::length = size;
和维度::长度=大小; in setname and setlength methods?
在setname和setlength方法中? You're in the scope of dimension class, aren't you?
您属于维度类的范围,不是吗?
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