Introduction

When you first open JUCE as a C++ developer trained on textbooks, it can feel… unconventional. Classes don’t have “Interface” or “Abstract” in the name. You won’t see every type annotated or prefixed. Members don’t start with m_. At first, it looks like the framework is skipping steps, ignoring patterns, doing its own thing - maybe even giving the finger to the greybeards of old. (And yes, it’s refreshingly not using COM: no GUIDs, no HRESULTs, no boilerplate that doubles as a test of your patience.)

When you dig a little deeper, you notice the design is deliberate: JUCE follows SOLID, DRY, and RAII principles, among the many you’re already familiar with - it’s just abstracted. The patterns exist, but they’re implicit; you don’t need to label every class or add a dozen extra layers just to signal intent. The code itself communicates the design.

It’s like reading a book without having to prefix every word with its part of speech: you don’t see vWrite for a verb or nTable for a noun - you just read and understand what’s happening. It feels cleaner, faster, and honestly… liberating - you’ve internalised it without reading through several layers of encoded flaming hoops.

Intent without Ceremony

Basically, this means that the purpose of the code is immediately clear. You can see what it does without wading through boilerplate, extra keywords, or unnecessary layers of abstraction.

Implicit Patterns in JUCE.

One of the things that surprises new JUCE developers is how patterns appear implicitly. You won’t see a class called IButtonListener or a prefix screaming Observer - but the patterns are *there*, made very clear once you understand the framework.

Example 1: ListenerList is the Observer Pattern

class MyComponent final : public juce::Component
{
public:
    // [Prior, surely important code beforehand.]

    class MyListener
    {
    public:
        virtual ~MyListener() noexcept = default;

        virtual void somethingChanged() = 0;
    };

    void addListener (MyListener* listener)     { listeners.add (listener); }
    void removeListener (MyListener* listener)  { listeners.remove (listener); }

protected:
    void notifySomethingChanged()
    {
        listeners.call ([](MyListener& l) { l.somethingChanged(); });
    }

private:
    juce::ListenerList<MyListener> listeners;
};

Here, ListenerList is JUCE’s implementation of the observer pattern. There’s no extra interface boilerplate, no template gymnastics, and no verbose registration system. It’s simple, readable, and gets the job done - the pattern is abstracted, but obvious in context.

Example 2: Reference Counting via ReferenceCountedObject

class MyData : public juce::ReferenceCountedObject
{
public:
    using Ptr = juce::ReferenceCountedObjectPtr<MyData>;

    // [Your fancy code here.]
};

This is JUCE’s historical approach to std::shared_ptr. You don’t see std::shared_ptr everywhere, but the memory management is clear and automatic. You don’t have to annotate or prefix anything; the intent is communicated by the code structure itself.

Example 3: AudioFormatReader / AudioFormatWriter are Façade Patterns

juce::AudioFormatManager formatManager;
formatManager.registerBasicFormats();

std::unique_ptr<juce::AudioFormatReader> reader (formatManager.createReaderFor (juce::File ("C:/MySongs/MySong1.wav")));

if (reader != nullptr)
{
    // use the reader to access audio data
}
else
{
    jassertfalse; // Couldn't load the file, invalid codec, unknown codec, etc...
}
  • The juce::AudioFormatManager acts as a factory, producing readers for whatever file format is needed.
  • Each juce::AudioFormatReader / juce::AudioFormatWriter acts as a façade, providing a simplified interface to complex subsystems that handle different audio formats and codecs.
  • You don’t need to know the internal details of WAV, AIFF, or MP3 decoding - the reader hides all that complexity behind a clean, easy-to-use interface.

Example 4: juce::Value is a Proxy Pattern

juce::Value volume;
volume.addListener (this);        // Observer baked in
volume = 0.8f;                    // Updates underlying value to 0.8f
float currentVolume = volume;     // Reads value through the proxy
  • Acts as a proxy for an underlying data item.
  • You can read/write the value without touching the storage directly.
  • Listeners automatically see changes (caller/controller dependent) - no boilerplate needed.

Example 5: LookAndFeel is a Decorator Pattern

class MyLookAndFeel final : public juce::LookAndFeel_V4
{
public:
    void drawButtonBackground (juce::Graphics& g, juce::Button&, const juce::Colour&, bool, bool) override
    {
        g.fillAll (juce::Colours::hotpink);
    }
};

juce::TextButton button;
button.setLookAndFeel (&myLookAndFeel);
  • Lets you decorate existing components with custom drawing behaviour.
  • You override or augment specific functionality without touching the original component.
  • Implicit decorator - simple, readable, and practical.

Example 6: AudioIODeviceCallback is a Bridge Pattern

class MyAudioCallback : public juce::AudioIODeviceCallback
{
    void audioDeviceIOCallback (const float** inputChannelData, int numInputChannels,
                                float** outputChannelData, int numOutputChannels,
                                int numSamples) override
    {
        // processing logic
    }
};

device->start (&myCallback);
  • Decouples the audio device from the processing logic.
  • juce::AudioIODevice handles the hardware, while your callback handles the processing - a classic bridge.
  • Low-level, modern, and very explicit about intent without ceremony.

Example 7: JUCE_DECLARE_SINGLETON is (Obviously) a Singleton Pattern

struct MySingleton
{
    MySingleton() {}
    ~MySingleton()
    {
        clearSingletonInstance();
    }

    JUCE_DECLARE_SINGLETON (MySingleton, false)
};

// In a .cpp file:
JUCE_IMPLEMENT_SINGLETON (MySingleton)

// Usage:
if (auto* instance = MySingleton::getInstance())
{
    // use the singleton
}
  • Ironically not implicit - it doesn’t get any more obvious than that!
  • The macros handle the usual singleton boilerplate: static storage, lazy instantiation, safe cleanup, threadedness needs…
  • getInstance() provides controlled global access.
  • clearSingletonInstance() in the destructor avoids dangling pointers.
  • Demonstrates the singleton pattern in a pragmatic, readable, low‑ceremony JUCE style.

Code as Plain English

This is the real magic of JUCE: once you understand these implicit patterns, the code reads almost like plain English.

MyData::Ptr p = new MyData();                                  // You know this is a ref-counted - JUCE based - pointer object instance.
component.addListener (&myObject);                             // You know this is a JUCE Component adding a ComponentListener.
listeners.call ([] (MyListener& l) { l.somethingChanged(); }); // You know this is a juce::ListenerList notifying the registered listeners about somethingChanged().

You don’t need to constantly translate naming conventions, guess at type annotations, or interpret verbose boilerplate. The code communicates its purpose directly, which makes it easier to read, maintain, and extend. Communication is a core principle here - the framework is designed so the code itself is the primary medium of understanding.

Closing Thoughts

JUCE isn’t about following patterns for the sake of labels or ceremony. It’s about practical, readable, and maintainable code that communicates its intent clearly. The patterns - observer, reference counting, RAII, factory, facade, and more - they’re all there. They’re just abstracted in a way that lets you focus on what the code does, not how it’s named. For developers willing to learn the framework’s idioms, this approach pays off with faster iteration and cleaner design, resulting in code that reads in a straightforward and human-centric way.

In the end, JUCE rewards pragmatism over formality - and that’s a lesson any reasonable software developer can appreciate.