UE学习日志#7 GAS--ASC源码简要分析5 GameplayEffects: Primary outward facing API for other systems P1

注：1.这个分类是按照源码里的注释分类的

2.本篇是通读并给出一些注释形式的，并不涉及结构性的分析

3.看之前要对UE的GAS系统的定义有初步了解

1 ApplyGameplayEffectSpecToTarget/Self

1.1 ApplyGameplayEffectSpecToTarget        

应用一个已经创建的GameplayEffectSpec到目标，指向的是ASC

声明：

/** Applies a previously created gameplay effect spec to a target */
UFUNCTION(BlueprintCallable, Category = GameplayEffects, meta = (DisplayName = "ApplyGameplayEffectSpecToTarget", ScriptName = "ApplyGameplayEffectSpecToTarget"))
FActiveGameplayEffectHandle BP_ApplyGameplayEffectSpecToTarget(const FGameplayEffectSpecHandle& SpecHandle, UAbilitySystemComponent* Target);

virtual FActiveGameplayEffectHandle ApplyGameplayEffectSpecToTarget(const FGameplayEffectSpec& GameplayEffect, UAbilitySystemComponent *Target, FPredictionKey PredictionKey=FPredictionKey());

下面是实现：

1.SCOPE_CYCLE_COUNTER是系统中用来性能分析的，会记录执行时间

2.ShouldPredictTargetGameplayEffects() 是一个全局配置函数，用于判断是否需要对目标效果进行预测
如果全局配置中明确不需要预测目标效果，则将 PredictionKey重设为默认的构造（预测允许客户端提前执行某些操作，并在后续与服务器同步时修正结果，从而减少玩家感知到的延迟）

3.Target调用ApplyGameplayEffectSpecToSelf,并返回Handle

FActiveGameplayEffectHandle UAbilitySystemComponent::ApplyGameplayEffectSpecToTarget(const FGameplayEffectSpec &Spec, UAbilitySystemComponent *Target, FPredictionKey PredictionKey)
{
	SCOPE_CYCLE_COUNTER(STAT_AbilitySystemComp_ApplyGameplayEffectSpecToTarget);
	UAbilitySystemGlobals& AbilitySystemGlobals = UAbilitySystemGlobals::Get();

	if (!AbilitySystemGlobals.ShouldPredictTargetGameplayEffects())
	{
		// If we don't want to predict target effects, clear prediction key
		PredictionKey = FPredictionKey();
	}

	FActiveGameplayEffectHandle ReturnHandle;

	if (Target)
	{
		ReturnHandle = Target->ApplyGameplayEffectSpecToSelf(Spec, PredictionKey);
	}

	return ReturnHandle;
}

1.2 ApplyGameplayEffectSpecToSelf

声明：

/** Applies a previously created gameplay effect spec to this component */
UFUNCTION(BlueprintCallable, Category = GameplayEffects, meta = (DisplayName = "ApplyGameplayEffectSpecToSelf", ScriptName = "ApplyGameplayEffectSpecToSelf"))
FActiveGameplayEffectHandle BP_ApplyGameplayEffectSpecToSelf(const FGameplayEffectSpecHandle& SpecHandle);

virtual FActiveGameplayEffectHandle ApplyGameplayEffectSpecToSelf(const FGameplayEffectSpec& GameplayEffect, FPredictionKey PredictionKey = FPredictionKey());

实现太长了，分段看：

（注释写在代码块里了）

#if WITH_SERVER_CODE
	SCOPE_CYCLE_COUNTER(STAT_AbilitySystemComp_ApplyGameplayEffectSpecToSelf);
#endif
//还是同上，用于性能分析

	// Scope lock the container after the addition has taken place to prevent the new effect from potentially getting mangled during the remainder
	// of the add operation
	FScopedActiveGameplayEffectLock ScopeLock