我有一些很好的老式c风格字符串列表:
const char * p1key = PROPERTY_MAX_THREADS;
const char * p1value = "12";
const char * p2key = PROPERTY_MAX_FRAMES;
const char * p2value = "400";
const char * p3key = PROPERTY_MAX_FRAMEMEMORY;
const char * p3value = "140";
...
然后我和他们做了一些事情:
// write p1, p2, p3, pn to disk in fancy format
最后,我希望能够编写循环并将写入的值与原始值进行比较。
int numProperties = 20;
for (int i = 0; i < numProperties; ++i) {
// on the first iteration, access p1 key/value
// on the second, access p2 key/value
// ...
}
如何在第一次迭代中访问p1,在第二次迭代时访问p2等?一系列指针会有帮助吗?我正在努力想出使其成功的语法。任何帮助将非常感谢。
我会考虑显示C和C ++方式的最佳答案
答案 0 :(得分:3)
<强>引言强>
您必须将指针存储在某种容器中,以便能够按照您的建议迭代它们。
由于你正在处理对,std::pair
<utility>
似乎是一个完美的匹配。将这些std::pair
包装在std::vector
等容器中,可以很容易地以干净的方式迭代它们。
示例实施
#include <iostream>
#include <utility>
#include <vector>
#define PROPERTY_MAX_THREADS "max_threads"
#define PROPERTY_MAX_FRAMES "max_frames"
#define PROPERTY_MAX_FRAMEMEMORY "max_fmemory"
const char * p1key = PROPERTY_MAX_THREADS;
const char * p1value = "12";
const char * p2key = PROPERTY_MAX_FRAMES;
const char * p2value = "400";
const char * p3key = PROPERTY_MAX_FRAMEMEMORY;
const char * p3value = "140";
int
main (int argc, char *argv[])
{
std::vector<std::pair<char const *, char const *>> properties {
{ p1key, p1value }, { p2key, p2value }, { p3key, p3value }
};
std::cout << "properties:\n";
for (auto& it : properties) {
std::cout << " " << it.first << " = " << it.second << "\n";
}
}
properties:
max_threads = 12
max_frames = 400
max_fmemory = 140
我在上面做过但我做过编程,为什么?
以前编写的代码片段使用了C ++ 11中引入的功能,如果您无法编译此类代码,则需要使用编译器提供的功能。
下面是一个修改过的实现,可以由任何支持C ++ 03的编译器编译:
int const PROPERTIES_LEN = 3;
std::pair<char const *, char const*> properties[PROPERTIES_LEN] = {
std::make_pair (p1key, p1value),
std::make_pair (p2key, p2value),
std::make_pair (p3key, p3value)
};
for (int i = 0; i < PROPERTIES_LEN; ++i) {
std::cout << properties[i].first << " = " << properties[i].second << "\n";
}
答案 1 :(得分:2)
你把它标记为C ++,所以我要提出C ++建议。
#include <iostream>
#include <vector>
#include <utility>
#define PROPERTY_MAX_THREADS "1"
#define PROPERTY_MAX_FRAMES "2"
#define PROPERTY_MAX_FRAMEMEMORY "3"
const char * p1key = PROPERTY_MAX_THREADS;
const char * p1value = "12";
const char * p2key = PROPERTY_MAX_FRAMES;
const char * p2value = "400";
const char * p3key = PROPERTY_MAX_FRAMEMEMORY;
const char * p3value = "140";
int main() {
using namespace std;
vector<pair<const char*,const char *>> collection =
{{p1key,p1value},{p2key,p2value},{p3key,p3value}};
for(auto &ele : collection){
cout << "key:" << ele.first
<< "value:" << ele.second << endl;
}
return 0;
}
或者只是从头开始将其声明为一个集合
#include <iostream>
#include <string>
#include <vector>
#include <utility>
#define PROPERTY_MAX_THREADS "1"
#define PROPERTY_MAX_FRAMES "2"
#define PROPERTY_MAX_FRAMEMEMORY "3"
int main() {
using namespace std;
vector<pair<const string,const string>> collection =
{
{PROPERTY_MAX_THREADS, "12" },
{PROPERTY_MAX_FRAMES, "400"},
{PROPERTY_MAX_FRAMEMEMORY, "140"}
};
for(auto &ele : collection){
cout << "key:" << ele.first
<< " value:" << ele.second << endl;
}
return 0;
}
答案 2 :(得分:1)
在C中你可以这样做。
#define STRA_END 0
const char* keyArray[] = {
"string1",
"string2",
"string3",
STRA_END
}
const char* valueArray[] = {
"string1",
"string2",
"string3",
STRA_END
}
main(){
int i;
for( i=0; keyArray[i]!=0; ++i )
doSometingToString(keyArray[i], valueArray[i]);
}