I have a base class called Node
which defines two functions: indent
and toString
. The former will be used by all derived classes without overriding, however the latter will be overridden in the derived classes.
Node.hpp
#ifndef NODE_H
#define NODE_H
#include <string>
#include <vector>
#include <memory>
class Node {
public:
virtual std::string toString(int level) const {};
std::string indent(int level);
};
#endif
Node.cpp
#include "Node.hpp"
std::string Node::indent(int level) {
std::string indt;
for(int i = 0; i < level; i ) {
indt = "\t";
}
return indt;
}
I have a derived class FunctionNode
which wants to override toString
in node.hpp
.
FunctionNode.hpp
#ifndef FUNCTION_NODE_H
#define FUNCTION_NODE_H
#include "TypeNode.hpp"
#include "ParamsNode.hpp"
#include "BlockNode.hpp"
#include "DeclarationNode.hpp"
class FunctionNode : public DeclarationNode {
std::shared_ptr<TypeNode> type;
std::string name;
std::shared_ptr<ParamsNode> paramList;
std::shared_ptr<BlockNode> block;
public:
FunctionNode(std::shared_ptr<TypeNode> type,
const std::string &name,
std::shared_ptr<ParamsNode> paramList,
std::shared_ptr<BlockNode> block)
: type(std::move(type)), name(name),
paramList(std::move(paramList)), block(std::move(block)) {}
};
#endif
Note that DeclarationNode
is derived from Node
.
FunctionNode.cpp
#include "FunctionNode.hpp"
std::string FunctionNode::toString(int level) const override {
std::string indt = indent(level);
std::string s = indt "FunctionNode\n";
s = type->toString(level 1);
s = indt "\t" name "\n";
s = paramList->toString(level 1);
s = block->toString(level 1);
return s;
}
When I try to compile FunctionNode.cpp to an object using the following line in my Makefile.
FunctionNode.o: FunctionNode.cpp FunctionNode.hpp TypeNode.hpp ParamsNode.hpp BlockNode.hpp
I get the following error.
FunctionNode.cpp:3:55: error: expected function body after function declarator
std::string FunctionNode::toString(int level) const override {
^
But I have provided the function body. How do I fix this error?
CodePudding user response:
To override a function in a child class, you need to write the declaration in the class definition. The override specifier will only appear in the header file.
Header File
class FunctionNode : public DeclarationNode {
FunctionNode(...) { ... }
std::string toString(int level) const override;
};
Source File
#include "FunctionNode.hpp"
std::string FunctionNode::toString(int level) const {
...
}
CodePudding user response:
Your program has no return
statement for the method Node::toString
. Other than that there doesn't seem to by any other error except
fatal error: TypeNode.hpp: No such file or directory
since you didn't provide TypeNode.hpp
in your original question.
The program don't have the error you mentioned as can be seen here. If you can provide a minimal reproducible example and edit your question, it will be good. Note FunctionNode::toString
has also been declared inside the FunctionNode
class in the above link.