Gist for a Youtube video "How to declare and use Delegates in Unreal Engine 5"

TestClasses.cpp

#include "TestClasses.h"

DEFINE_LOG_CATEGORY_STATIC(TestClassSub, Log, All);

void UTestClass::InitDelegates() {
    _someDelegate1.BindStatic(&UTestClass::SomeStaticDelegateFunction);

    int hey = 5;
    _someDelegate2.BindLambda([hey](FString param) {
        UE_LOG(TestClassSub, Warning, TEXT("Lambda: %s, %d"), *param, hey);
    });

    _someDelegate3.BindWeakLambda(this, [](FString param) {
        UE_LOG(TestClassSub, Warning, TEXT("Lambda: %s"), *param);
    });

    SomeRawClass* someRawClass = new SomeRawClass();
    _someDelegate4.BindRaw(someRawClass, &SomeRawClass::SomeRawMethod);

    _someSharedPtr = TSharedPtr<SomeRawClass>(new SomeRawClass());
    _someDelegate5.BindSP(_someSharedPtr.ToSharedRef(), &SomeRawClass::SomeRawMethod);

    _someThreadSafeSharedPtr = TSharedPtr<SomeRawClass, ESPMode::ThreadSafe>(new SomeRawClass());
    _someDelegate6.BindThreadSafeSP(_someThreadSafeSharedPtr.ToSharedRef(), &SomeRawClass::SomeRawMethod);

    _someDelegate7.BindUFunction(this, TEXT("SomeDelegateUFunction"));

    _someDelegate8.BindUObject(this, &UTestClass::SomeDelegateUFunction);

    _someReturnValDelegate.BindLambda([](FString param) -> bool {
        UE_LOG(TestClassSub, Warning, TEXT("Lambda: %s"), *param);
        return true;
    });

/*
    AddStatic
    AddLambda
    AddWeakLambda
    AddRaw
    AddSP
    AddThreadSafeSP
    AddUFunction
    AddUObject
*/

    _someMulticastDelegate.AddLambda([hey](FString param) {
        UE_LOG(TestClassSub, Warning, TEXT("First Lambda: %s"), *param);
    });

    _someMulticastDelegate.AddLambda([hey](FString param) {
        UE_LOG(TestClassSub, Warning, TEXT("Second Lambda: %s"), *param);
    });

    FDelegateHandle handle = _someMulticastDelegate.AddLambda([hey](FString param) {
        UE_LOG(TestClassSub, Warning, TEXT("Not going to printed"), *param);
    });
    _someMulticastDelegate.Remove(handle);

    _someDynamicDelegate.BindDynamic(this, &UTestClass::SomeDelegateUFunction);

    _someDynamicMulticastDelegate.AddDynamic(this, &UTestClass::SomeDelegateUFunction);
    _someDynamicMulticastDelegate.RemoveDynamic(this, &UTestClass::SomeDelegateUFunction);
    
    _someDynamicMulticastDelegate.AddUniqueDynamic(this, &UTestClass::SomeDelegateUFunction);
}

void UTestClass::ExecuteDelegates() {
    _someDelegate1.Execute(TEXT("BindStatic"));
    _someDelegate2.Execute(TEXT("BindLambda"));
    _someDelegate3.Execute(TEXT("BindWeakLambda"));
    _someDelegate4.Execute(TEXT("BindRaw"));
    _someDelegate5.Execute(TEXT("BindSP"));
    _someDelegate6.Execute(TEXT("BindThreadSafeSP"));
    _someDelegate7.Execute(TEXT("BindUFunction"));
    _someDelegate8.Execute(TEXT("BindUObject"));

    bool returnVal = _someReturnValDelegate.Execute("ReturnValLambda");
    UE_LOG(TestClassSub, Warning, TEXT("Return val from lambda = %d"), returnVal);

    _someMulticastDelegate.Broadcast(TEXT("MulticastDelegate"));

    _someDynamicDelegate.Execute(TEXT("DynamicDelegate"));
    _someDynamicMulticastDelegate.Broadcast(TEXT("DynamicMulticast"));
}

void UTestClass::SomeStaticDelegateFunction(FString param) {
    UE_LOG(TestClassSub, Warning, TEXT("SomeStaticDelegateFunction: %s"), *param);
}

void UTestClass::SomeDelegateUFunction(FString param) {
    UE_LOG(TestClassSub, Warning, TEXT("SomeDelegateUFunction: %s"), *param);
}

void SomeRawClass::SomeRawMethod(FString param) {
    UE_LOG(TestClassSub, Warning, TEXT("SomeRawMethod: %s"), *param);
}

TestClasses.h

#pragma once

#include "CoreMinimal.h"
#include "Delegates/Delegate.h"
#include "TestClasses.generated.h"

DECLARE_DELEGATE_OneParam(FSomeDelegate, FString);
DECLARE_DELEGATE_RetVal_OneParam(bool, FSomeReturnValDelegate, FString);
DECLARE_MULTICAST_DELEGATE_OneParam(FSomeMulticastDelegate, FString);

DECLARE_DYNAMIC_DELEGATE_OneParam(FSomeDynamicDelegate, FString, param);
DECLARE_DYNAMIC_MULTICAST_DELEGATE_OneParam(FSomeDynamicMulticastDelegate, FString, param);

UCLASS()
class UTestClass : public UObject {
    GENERATED_BODY()

public:
    void InitDelegates();
    void ExecuteDelegates();

    static void SomeStaticDelegateFunction(FString param);

    UFUNCTION()
    void SomeDelegateUFunction(FString param);

private:
    FSomeDelegate _someDelegate1;
    FSomeDelegate _someDelegate2;
    FSomeDelegate _someDelegate3;
    FSomeDelegate _someDelegate4;
    FSomeDelegate _someDelegate5;
    FSomeDelegate _someDelegate6;
    FSomeDelegate _someDelegate7;
    FSomeDelegate _someDelegate8;

    FSomeReturnValDelegate _someReturnValDelegate;

    TSharedPtr<class SomeRawClass> _someSharedPtr;
    TSharedPtr<class SomeRawClass, ESPMode::ThreadSafe> _someThreadSafeSharedPtr;

    FSomeMulticastDelegate _someMulticastDelegate;

    FSomeDynamicDelegate _someDynamicDelegate;
    FSomeDynamicMulticastDelegate _someDynamicMulticastDelegate;
};

class SomeRawClass {
public:
    void SomeRawMethod(FString param);
};