Resolve "State key char instead of string"

Closes #352 (closed)

include/core/capture/capture_base.h

@@ -83,8 +83,7 @@ class CaptureBase : public NodeBase, public HasStateBlocks, public std::enable_s
 
         // State blocks
         const StateStructure& getStructure() const;
-        StateBlockPtr getStateBlock(const std::string& _key) const;
-        StateBlockPtr getStateBlock(const char _key) const { return getStateBlock(std::string(1, _key)); }
+        StateBlockPtr getStateBlock(const char& _key) const;
         StateBlockPtr getSensorP() const;
         StateBlockPtr getSensorO() const;
         StateBlockPtr getSensorIntrinsic() const;
@@ -138,17 +137,17 @@ std::shared_ptr<classType> CaptureBase::emplace(FrameBasePtr _frm_ptr, T&&... al
 
 inline StateBlockPtr CaptureBase::getSensorP() const
 {
-    return getStateBlock("P");
+    return getStateBlock('P');
 }
 
 inline StateBlockPtr CaptureBase::getSensorO() const
 {
-    return getStateBlock("O");
+    return getStateBlock('O');
 }
 
 inline StateBlockPtr CaptureBase::getSensorIntrinsic() const
 {
-    return getStateBlock("I");
+    return getStateBlock('I');
 }
 
 inline unsigned int CaptureBase::id() const