fixed predicate chaining bug

Author: jkalias

include/query_predicates.h

@@ -40,6 +40,9 @@ namespace sqlite_reflection {
 		/// Returns a textual representation of the predicate, ready to be consumed by the SELECT query
 		virtual std::string Evaluate() const = 0;
 
+		/// Creates a clone for compounding predicates
+		virtual QueryPredicateBase* Clone() const = 0;
+
 		/// Returns a compound predicate, which requires that both the current
 		/// and the other predicate are valid at the same time
 		AndPredicate And(const QueryPredicateBase& other) const;
@@ -56,11 +59,13 @@ namespace sqlite_reflection {
 	{
 	public:
 		std::string Evaluate() const override;
+		QueryPredicateBase* Clone() const override;
 
 	protected:
 		template <typename T, typename R>
-		QueryPredicate(R T::* fn, R value, const std::string& symbol, std::function<std::string(void*, SqliteStorageClass)> value_retrieval) {
-			symbol_ = symbol;
+		QueryPredicate(R T::* fn, R value, const std::string& symbol, std::function<std::string(void*, SqliteStorageClass)> value_retrieval)
+		: symbol_(symbol)
+		{
 			auto record = GetRecordFromTypeId(typeid(T).name());
 			auto offset = OffsetFromStart(fn);
 			for (auto i = 0; i < record.member_metadata.size(); ++i) {
@@ -78,6 +83,9 @@ namespace sqlite_reflection {
 				return GetStringForValue(v, storage_class);
 			}) {}
 
+		QueryPredicate(const std::string& symbol, const std::string& member_name, const std::string& value)
+			: symbol_(symbol), member_name_(member_name), value_(value) {}
+
 		/// Returns a textual representation of the value used for the current query, against which the
 		/// struct member (defined from the pointer-to-member function) will be compared. The value needs
 		/// to be type-erased, so that the header file is not bloated with unnecessary implementation details
@@ -100,6 +108,7 @@ namespace sqlite_reflection {
 	{
 	public:
 		std::string Evaluate() const override;
+		QueryPredicateBase* Clone() const override;
 	};
 
 	/// A wrapper for an equality predicate, for which the value of the
@@ -204,8 +213,8 @@ namespace sqlite_reflection {
 	protected:
 		BinaryPredicate(const QueryPredicateBase& left, const QueryPredicateBase& right, const std::string& symbol);
 
-		const QueryPredicateBase* left_;
-		const QueryPredicateBase* right_;
+		std::unique_ptr<QueryPredicateBase> left_;
+		std::unique_ptr<QueryPredicateBase> right_;
 		std::string symbol_;
 	};
 
@@ -214,12 +223,14 @@ namespace sqlite_reflection {
 	{
 	public:
 		AndPredicate(const QueryPredicateBase& left, const QueryPredicateBase& right);
+		QueryPredicateBase* Clone() const override;
 	};
 
 	/// A compound predicate, which requires that either predicate is valid
 	class REFLECTION_EXPORT OrPredicate final : public BinaryPredicate
 	{
 	public:
 		OrPredicate(const QueryPredicateBase& left, const QueryPredicateBase& right);
+		QueryPredicateBase* Clone() const override;
 	};
 }

src/query_predicates.cc

@@ -29,10 +29,18 @@ const std::string single_quote("'");
 const std::string space(" ");
 const std::string percent("%");
 
+QueryPredicateBase* QueryPredicate::Clone() const {
+	return new QueryPredicate(symbol_, member_name_, value_);
+}
+
 std::string EmptyPredicate::Evaluate() const {
 	return "";
 }
 
+QueryPredicateBase* EmptyPredicate::Clone() const {
+	return new EmptyPredicate();
+}
+
 AndPredicate QueryPredicateBase::And(const QueryPredicateBase& other) const {
 	return AndPredicate(*this, other);
 }
@@ -89,7 +97,7 @@ std::string Like::Remove(const std::string& source, const std::string& substring
 }
 
 BinaryPredicate::BinaryPredicate(const QueryPredicateBase& left, const QueryPredicateBase& right, const std::string& symbol)
-	: left_(&left), right_(&right), symbol_(symbol) {}
+	: left_(left.Clone()), right_(right.Clone()), symbol_(symbol) {}
 
 std::string BinaryPredicate::Evaluate() const {
 	return "(" + left_->Evaluate() + space + symbol_ + space + right_->Evaluate() + ")";
@@ -98,5 +106,13 @@ std::string BinaryPredicate::Evaluate() const {
 AndPredicate::AndPredicate(const QueryPredicateBase& left, const QueryPredicateBase& right)
 	: BinaryPredicate(left, right, "AND") {}
 
+QueryPredicateBase* AndPredicate::Clone() const {
+	return new AndPredicate(*left_.get(), *right_.get());
+}
+
 OrPredicate::OrPredicate(const QueryPredicateBase& left, const QueryPredicateBase& right)
 	: BinaryPredicate(left, right, "OR") {}
+
+QueryPredicateBase* OrPredicate::Clone() const {
+	return new OrPredicate(*left_.get(), *right_.get());
+}