问题描述
我想要能够创建一个函数,其中我指定一个参数,同时拥有一个模板容器和该容器的模板元素类型。这可能吗?我得到错误C2988:不可扩展的模板声明/定义等。
模板< class Iter,Elem>
void readIntoP(Iter< Elem> aCont){
ifstream ifss(data.dat);
string aString;
int counter = 0;
item tempItem;
while(ifss>> aString){
istringstream iss(aString);
if(counter == 0){
tempItem.name = aString;
} else if(counter == 1){
int aNum = 0;
iss>> aNum;
tempItem.iid = aNum;
} else {
double aNum = 0;
iss>> aNum;
tempItem.value = aNum;
aCont.push_back(tempItem);
counter = -1;
}
++ counter;
}
}
template< template< class> class Iter,class Elem>
void readIntoP(Iter< Elem> aCont){/ * ... * /}
但是,请注意,标准库容器需要多个模板参数(向量
,例如,需要两个:一个用于存储值类型,一个用于分配器
您可以为实例化的容器类型使用一个模板参数,然后使用 value_type
typedef :
模板< typename ContainerT>
void readIntoP(ContainerT aCont)
{
typedef typename ContainerT :: value_type ElementT;
//使用ContainerT和ElementT
}
I want to be able to create a function where I specify a parameter to have both a templated container and a templated element type for that container. Is this possible? I get "error C2988: unrecongnizable template declaration/definition" among others. Here is the function in question.
template<class Iter, class Elem>
void readIntoP(Iter<Elem> aCont){
ifstream ifss("data.dat");
string aString;
int counter = 0;
item tempItem;
while(ifss >> aString){
istringstream iss(aString);
if(counter == 0){
tempItem.name = aString;
}else if(counter == 1){
int aNum = 0;
iss >> aNum;
tempItem.iid = aNum;
}else{
double aNum = 0;
iss >> aNum;
tempItem.value = aNum;
aCont.push_back(tempItem);
counter = -1;
}
++counter;
}
}
You would need to use a template template parameter, e.g.,
template <template <class> class Iter, class Elem>
void readIntoP(Iter<Elem> aCont) { /* ... */ }
Note, however, that the standard library containers take multiple template parameters (vector
, for example, takes two: one for the value type to be stored and one for the allocator to use).
You might instead use a single template parameter for the instantiated container type and then use its value_type
typedef:
template <typename ContainerT>
void readIntoP(ContainerT aCont)
{
typedef typename ContainerT::value_type ElementT;
// use ContainerT and ElementT
}
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