[英]Array initialization in c++
I'm new to C++, and I want to know if this valid. 我是C ++的新手,我想知道这是否有效。
So I want to create an array of strings, but I wont know the size of the array I need until a value is passed in to a function within the class I'm working in. So, can I do this: 因此,我想创建一个字符串数组,但是在将值传递给正在使用的类中的函数之前,我不知道需要的数组大小。因此,我可以这样做:
string sList[];
void init(unsigned int size=1)
{
sList = new string[size];
}
I'm sorry if this is a dumb question, but I'm a Java guy new to C++. 如果这是一个愚蠢的问题,我感到抱歉,但是我是C ++的Java新手。
EDIT: This is an assignment that involves me writing an array wrapper class. 编辑:这是一项涉及我编写数组包装器类的任务。 If I could use vector<>, trust me, I would.
如果我可以使用vector <>,请相信我。
This is correct, although string sList[]
should be string *sList
. 这是正确的,尽管
string sList[]
应该是string *sList
。 Don't forget the delete [] sList
at the end. 不要忘记最后的
delete [] sList
。
As many others say, you can use std::vector
if you want, but getting some practice with arrays is an excellent way to learn how the memory management works and I encourage you to explore it further. 就像许多其他人所说的那样,您可以根据需要使用
std::vector
,但是对数组进行一些练习是了解内存管理如何工作的绝佳方法,我鼓励您进一步探索它。
A new-expression (such as new string[size]
) returns a pointer to a dynamically allocated object. new表达式 (例如
new string[size]
)返回一个指向动态分配对象的指针。 In this case, it returns a pointer to the first string
object in the dynamically allocated array. 在这种情况下,它返回一个指向动态分配数组中第一个
string
对象的指针。 So to make this work, sList
should be a pointer: 因此,要使其工作,
sList
应该是一个指针:
string* sList;
It is important to remember that you must always delete
/ delete[]
and object that has been created with new
/ new[]
. 重要的是要记住,必须始终
delete
/ delete[]
和使用new
/ new[]
创建的对象。 So you must at some point delete[] sList
. 因此,您必须在某些时候
delete[] sList
。 If you don't do this, the memory allocated for the array of string
s will “never” be deallocated. 如果不这样做,分配给
string
s的内存将“从不”释放。
However, you'll be in a much better situation if you use a std::vector<std::string>
instead, rather than doing your own dynamic allocation. 但是,如果您使用
std::vector<std::string>
而不是自己进行动态分配,则情况会更好。
The right way to do this in C++: 在C ++中执行此操作的正确方法:
#include <string>
#include <vector>
std::vector<std::string> sList;
void init(unsigned int size = 1)
{
sList.resize(size);
}
int main()
{
init(25);
}
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