How can I initialize a static const string of a template for each class type the templated class creates?
-1
My (broken) code:
// hpp file
#include <iostream>
#include <string>
class iHello {
public: virtual void hello(void) = 0;
};
template<typename T> class foo : public iHello {
public: void hello(void) { std::cout << "Say hello :" << key << std::endl; }
private:
static const std::string key;
};
template<typename T> const std::string foo<T>::key = "all foo<T>";
// cpp file
class boo: public foo<boo> { };
class bar: public foo<bar> { };
template<typename T> const std::string foo<bar>::key = "bar"; // error
class baz: public foo<baz> { };
template<typename T> const std::string foo<baz>::key = "baz"; // error
int main(int argc, char ** argv) {
boo a;
bar b;
baz c;
a.hello();
b.hello();
c.hello();
return 0;
}
My desired output would be:
Say hello :all foo<T>
Say hello :bar
Say hello :baz
But I can't figure out how to initialize the static constant member key based on the templated class.
If I can't do both (general and specific cases), then my preference is that I would have to explicitly define key for each templated class created.
Is there a way to do this?
c++ c++11 templates
asked Nov 16 '18 at 2:11
JamieJamie
3,25174375
add a comment |
-1
My (broken) code:
// hpp file
#include <iostream>
#include <string>
class iHello {
public: virtual void hello(void) = 0;
};
template<typename T> class foo : public iHello {
public: void hello(void) { std::cout << "Say hello :" << key << std::endl; }
private:
static const std::string key;
};
template<typename T> const std::string foo<T>::key = "all foo<T>";
// cpp file
class boo: public foo<boo> { };
class bar: public foo<bar> { };
template<typename T> const std::string foo<bar>::key = "bar"; // error
class baz: public foo<baz> { };
template<typename T> const std::string foo<baz>::key = "baz"; // error
int main(int argc, char ** argv) {
boo a;
bar b;
baz c;
a.hello();
b.hello();
c.hello();
return 0;
}
My desired output would be:
Say hello :all foo<T>
Say hello :bar
Say hello :baz
But I can't figure out how to initialize the static constant member key based on the templated class.
If I can't do both (general and specific cases), then my preference is that I would have to explicitly define key for each templated class created.
Is there a way to do this?
c++ c++11 templates
asked Nov 16 '18 at 2:11
JamieJamie
3,25174375
2
You just needtemplate<>when doing an explicit specialization.
– 0x499602D2
Nov 16 '18 at 2:13
@0x499602D2 You, sir/madame, have the answer. (but I can't mark your comment as the such)
– Jamie
Nov 16 '18 at 2:18
add a comment |
-1
-1
-1
My (broken) code:
// hpp file
#include <iostream>
#include <string>
class iHello {
public: virtual void hello(void) = 0;
};
template<typename T> class foo : public iHello {
public: void hello(void) { std::cout << "Say hello :" << key << std::endl; }
private:
static const std::string key;
};
template<typename T> const std::string foo<T>::key = "all foo<T>";
// cpp file
class boo: public foo<boo> { };
class bar: public foo<bar> { };
template<typename T> const std::string foo<bar>::key = "bar"; // error
class baz: public foo<baz> { };
template<typename T> const std::string foo<baz>::key = "baz"; // error
int main(int argc, char ** argv) {
boo a;
bar b;
baz c;
a.hello();
b.hello();
c.hello();
return 0;
}
My desired output would be:
Say hello :all foo<T>
Say hello :bar
Say hello :baz
But I can't figure out how to initialize the static constant member key based on the templated class.
If I can't do both (general and specific cases), then my preference is that I would have to explicitly define key for each templated class created.
Is there a way to do this?
c++ c++11 templates
asked Nov 16 '18 at 2:11
JamieJamie
3,25174375
My (broken) code:
// hpp file
#include <iostream>
#include <string>
class iHello {
public: virtual void hello(void) = 0;
};
template<typename T> class foo : public iHello {
public: void hello(void) { std::cout << "Say hello :" << key << std::endl; }
private:
static const std::string key;
};
template<typename T> const std::string foo<T>::key = "all foo<T>";
// cpp file
class boo: public foo<boo> { };
class bar: public foo<bar> { };
template<typename T> const std::string foo<bar>::key = "bar"; // error
class baz: public foo<baz> { };
template<typename T> const std::string foo<baz>::key = "baz"; // error
int main(int argc, char ** argv) {
boo a;
bar b;
baz c;
a.hello();
b.hello();
c.hello();
return 0;
}
My desired output would be:
Say hello :all foo<T>
Say hello :bar
Say hello :baz
But I can't figure out how to initialize the static constant member key based on the templated class.
If I can't do both (general and specific cases), then my preference is that I would have to explicitly define key for each templated class created.
Is there a way to do this?
c++ c++11 templates
c++ c++11 templates
asked Nov 16 '18 at 2:11
JamieJamie
3,25174375
asked Nov 16 '18 at 2:11
JamieJamie
3,25174375
edited Nov 16 '18 at 2:16
Jamie
asked Nov 16 '18 at 2:11
JamieJamie
3,25174375
asked Nov 16 '18 at 2:11
JamieJamie
3,25174375
asked Nov 16 '18 at 2:11
JamieJamie
3,25174375
3,25174375
2
You just needtemplate<>when doing an explicit specialization.
– 0x499602D2
Nov 16 '18 at 2:13
@0x499602D2 You, sir/madame, have the answer. (but I can't mark your comment as the such)
– Jamie
Nov 16 '18 at 2:18
add a comment |
2
You just needtemplate<>when doing an explicit specialization.
– 0x499602D2
Nov 16 '18 at 2:13
@0x499602D2 You, sir/madame, have the answer. (but I can't mark your comment as the such)
– Jamie
Nov 16 '18 at 2:18
2
2
You just need
template<> when doing an explicit specialization.– 0x499602D2
Nov 16 '18 at 2:13
You just need
template<> when doing an explicit specialization.– 0x499602D2
Nov 16 '18 at 2:13
@0x499602D2 You, sir/madame, have the answer. (but I can't mark your comment as the such)
– Jamie
Nov 16 '18 at 2:18
@0x499602D2 You, sir/madame, have the answer. (but I can't mark your comment as the such)
– Jamie
Nov 16 '18 at 2:18
add a comment |
1 Answer
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The correct syntax for full specialization of static members in definition should be:
template<> const std::string foo<bar>::key = "bar";
template<> const std::string foo<baz>::key = "baz";
answered Nov 16 '18 at 2:18
songyuanyaosongyuanyao
93.1k11182247
add a comment |
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1 Answer
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1 Answer
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oldest
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oldest
votes
1
The correct syntax for full specialization of static members in definition should be:
template<> const std::string foo<bar>::key = "bar";
template<> const std::string foo<baz>::key = "baz";
answered Nov 16 '18 at 2:18
songyuanyaosongyuanyao
93.1k11182247
add a comment |
1
The correct syntax for full specialization of static members in definition should be:
template<> const std::string foo<bar>::key = "bar";
template<> const std::string foo<baz>::key = "baz";
answered Nov 16 '18 at 2:18
songyuanyaosongyuanyao
93.1k11182247
add a comment |
1
1
1
The correct syntax for full specialization of static members in definition should be:
template<> const std::string foo<bar>::key = "bar";
template<> const std::string foo<baz>::key = "baz";
answered Nov 16 '18 at 2:18
songyuanyaosongyuanyao
93.1k11182247
The correct syntax for full specialization of static members in definition should be:
template<> const std::string foo<bar>::key = "bar";
template<> const std::string foo<baz>::key = "baz";
answered Nov 16 '18 at 2:18
songyuanyaosongyuanyao
93.1k11182247
answered Nov 16 '18 at 2:18
songyuanyaosongyuanyao
93.1k11182247
answered Nov 16 '18 at 2:18
songyuanyaosongyuanyao
93.1k11182247
answered Nov 16 '18 at 2:18
songyuanyaosongyuanyao
93.1k11182247
93.1k11182247
add a comment |
add a comment |
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2
You just need
template<>when doing an explicit specialization.– 0x499602D2
Nov 16 '18 at 2:13
@0x499602D2 You, sir/madame, have the answer. (but I can't mark your comment as the such)
– Jamie
Nov 16 '18 at 2:18