# Error C2259: cannot instantiate abstract class **URL:** \ **Category:** General JUCE discussion\ **Created:** [February 26, 2014, 6:15pm UTC](https://forum.juce.com/t/error-c2259-cannot-instantiate-abstract-class/12457 "2014-02-26T18:15:41Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![mihnea](https://avatars.discourse-cdn.com/v4/letter/m/9fc29f/32.png) [@mihnea](https://forum.juce.com/u/mihnea)\ **Post date:** [February 26, 2014, 6:15pm UTC](https://forum.juce.com/t/error-c2259-cannot-instantiate-abstract-class/12457/1 "2014-02-26T18:15:41Z")
Hi everybody! I am new to C++ and Juce but I need to use it for a Uni module. I have searched for similar errors/issues by other users but couldn't find an answer that may be able to fix my problem. Long story short: I am trying to build a simple compressor but I get the forementioned error: 2259: cannot instantiate abstract class. I am trying to build it with Visual Studio 2012 which points at the bolded lines, does anyone have any ideas as to what is causing the error? I apologize if it sounds like a noob question but I really like Juce and would like to experiment with it but can't get past this...   Best, M.   > // This creates new instances of the plugin.. > **AudioProcessor\* JUCE\_CALLTYPE createPluginFilter() > { >     return new CompressorAudioProcessor(); > }** > > int CompressorAudioProcessor::round(float inn) > { >     if (inn \> 0) return (int) (inn + 0.5); >     else return (int) (inn - 0.5); > } > const String CompressorAudioProcessor::getName() const > { >     return JucePlugin\_Name; > } > int CompressorAudioProcessor::getNumParameters() > { >     return 0; > } > float CompressorAudioProcessor::getParameter (int index) > { >     return 0.0f; > } > void CompressorAudioProcessor::setParameter (int index, float newValue) > { > } > const String CompressorAudioProcessor::getParameterName (int index) > { >     return String::empty; > } > const String CompressorAudioProcessor::getParameterText (int index) > { >     return String::empty; > } > const String CompressorAudioProcessor::getInputChannelName (int channelIndex) const > { >     return String (channelIndex + 1); > } > const String CompressorAudioProcessor::getOutputChannelName (int channelIndex) const > { >     return String (channelIndex + 1); > } > bool CompressorAudioProcessor::isInputChannelStereoPair (int index) const > { >     return true; > } > bool CompressorAudioProcessor::isOutputChannelStereoPair (int index) const > { >     return true; > } > bool CompressorAudioProcessor::acceptsMidi() const > { > #if JucePlugin\_WantsMidiInput >     return true; > #else >     return false; > #endif > } > bool CompressorAudioProcessor::producesMidi() const > { > #if JucePlugin\_ProducesMidiOutput >     return true; > #else >     return false; > #endif > } > int CompressorAudioProcessor::getNumPrograms() > { >     return 0; > } > int CompressorAudioProcessor::getCurrentProgram() > { >     return 0; > } > void CompressorAudioProcessor::setCurrentProgram (int index) > { > } > const String CompressorAudioProcessor::getProgramName (int index) > { >     return String::empty; > } > void CompressorAudioProcessor::changeProgramName (int index, const String& newName) > { > } >   ---
**Author:** ![jrlanglois](https://sea2.discourse-cdn.com/flex026/user_avatar/forum.juce.com/jrlanglois/32/21372_2.png) [@jrlanglois](https://forum.juce.com/u/jrlanglois)\ **Post date:** [February 26, 2014, 6:18pm UTC](https://forum.juce.com/t/error-c2259-cannot-instantiate-abstract-class/12457/2 "2014-02-26T18:18:23Z")
Well, this error is a basic C++ one: you ain't filling out the pure-virtual methods from the base class (or classes). Any struct/class method marked with "= 0" at the end is stating that it is pure-virtual. Your error should state which one(s). (Though MSVC errors are so damned ugly and take some getting used to - it may not be obvious.) ---
**Author:** ![mihnea](https://avatars.discourse-cdn.com/v4/letter/m/9fc29f/32.png) [@mihnea](https://forum.juce.com/u/mihnea)\ **Post date:** [February 26, 2014, 6:33pm UTC](https://forum.juce.com/t/error-c2259-cannot-instantiate-abstract-class/12457/3 "2014-02-26T18:33:31Z")
I realize it might be an obvious one but I cannot figure it out. Here's the full error: > 1\>..\..\Source\PluginProcessor.cpp(172): error C2259: 'CompressorAudioProcessor' : cannot instantiate abstract class > 1\>          due to following members: > 1\>          'bool juce::AudioProcessor::silenceInProducesSilenceOut(void) const' : is abstract > 1\>          \res\juce\modules\juce\_audio\_processors\processors/juce\_AudioProcessor.h(249) : see declaration of 'juce::AudioProcessor::silenceInProducesSilenceOut' > 1\>          'double juce::AudioProcessor::getTailLengthSeconds(void) const' : is abstract > 1\>          \res\juce\modules\juce\_audio\_processors\processors/juce\_AudioProcessor.h(252) : see declaration of 'juce::AudioProcessor::getTailLengthSeconds' Any thoughts? ---
**Author:** ![jrlanglois](https://sea2.discourse-cdn.com/flex026/user_avatar/forum.juce.com/jrlanglois/32/21372_2.png) [@jrlanglois](https://forum.juce.com/u/jrlanglois)\ **Post date:** [February 26, 2014, 6:58pm UTC](https://forum.juce.com/t/error-c2259-cannot-instantiate-abstract-class/12457/4 "2014-02-26T18:58:27Z")
So, let me reword the error message, because the same error happens multiple times: > The class is still abstract, you need to fill out the following methods as they are missing: > > - "bool juce::AudioProcessor::silenceInProducesSilenceOut(void) const" > > - "double juce::AudioProcessor::getTailLengthSeconds(void) const" Hopefully this will help get you going! ---
**Author:** ![mihnea](https://avatars.discourse-cdn.com/v4/letter/m/9fc29f/32.png) [@mihnea](https://forum.juce.com/u/mihnea)\ **Post date:** [February 27, 2014, 6:54pm UTC](https://forum.juce.com/t/error-c2259-cannot-instantiate-abstract-class/12457/5 "2014-02-27T18:54:37Z")
Still no luck but I get the following error now: ![](https://dl.dropboxusercontent.com/u/1757767/Screenshot%202014-02-27%2018.49.15.png) Thoughts? ---
**Author:** ![oxxyyd](https://avatars.discourse-cdn.com/v4/letter/o/e47c2d/32.png) [@oxxyyd](https://forum.juce.com/u/oxxyyd)\ **Post date:** [February 27, 2014, 7:12pm UTC](https://forum.juce.com/t/error-c2259-cannot-instantiate-abstract-class/12457/6 "2014-02-27T19:12:50Z")
http://stackoverflow.com/questions/1306778/c-virtual-pure-virtual-explained