本文主要是介绍C 语言链式调用与Tween算法实现(4)链式封装接口，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
在有上下文this指针的语言中，可以把this指针return出去。这样就可以形成一种链式调用的效果。配合上良好的方法命名，能够让函数功能的组合调用，使用起来非常的直觉化。在C语言中并没有this指针，所有的上下文对象需要，手动传入上下文对象。
以前介绍了3篇关于C语言如何实现tween缓动算法的。
- C 实现通用Tween缓动动画(1)插值公式
- C 实现通用Tween缓动动画(2)Tween数据结构
然而，函数的调用缺少链式调用非常的不流畅。而tween又很多默认参数的设定，往往链式调用能够更加方便的使用。
本文结合一种实现链式调用的方式，来在tween的实现之上进行一个链式调用的封装。我的思路很简单，链式调用需要上下文，C没有，那我们就要构造一个上下文以供使用。那我们看代码。
struct ATweenTool
{/*** Create one TweenAction in context for chain setting*/struct ATweenTool* (*SetAction) ();/*** Create action with no actionValue* just through duration time then callback*/struct ATweenTool* (*SetInterval) (float duration);//--------------------------------------------------------------------------------------------------
// Create one TweenAction with TweenActionValue
//--------------------------------------------------------------------------------------------------struct ATweenTool* (*SetActionMoveX) (float moveX, float duration);struct ATweenTool* (*SetActionMoveY) (float moveY, float duration);struct ATweenTool* (*SetActionMove) (float moveX, float moveY, float duration, bool isRelative, TweenEaseType easeType);struct ATweenTool* (*SetActionScaleX) (float scaleX, float duration);struct ATweenTool* (*SetActionScaleY) (float scaleY, float duration);struct ATweenTool* (*SetActionScale) (float scaleX, float scaleY, float duration, bool isRelative, TweenEaseType easeType);struct ATweenTool* (*SetActionRotateZ)(float rotateZ, float duration);struct ATweenTool* (*SetActionFadeTo) (float fadeTo, float duration);//--------------------------------------------------------------------------------------------------
// After SetAction then set TweenAction property for current context created
//--------------------------------------------------------------------------------------------------struct ATweenTool* (*SetDuration) (float duration);struct ATweenTool* (*SetUserData) (void* userData);struct ATweenTool* (*SetQueue) (bool isQueue);struct ATweenTool* (*SetOnComplete) (TweenActionOnComplete OnComplete);struct ATweenTool* (*SetTarget) (void* target);/*** Get TweenAction in current context*/struct ATweenTool* (*GetAction) (TweenAction** outActionPtr);//--------------------------------------------------------------------------------------------------
// Add new TweenActionValue into context TweenAction
//--------------------------------------------------------------------------------------------------struct ATweenTool* (*SetMoveX) (float moveX);struct ATweenTool* (*SetMoveY) (float moveY);struct ATweenTool* (*SetScaleX) (float scaleX);struct ATweenTool* (*SetScaleY) (float scaleY);struct ATweenTool* (*SetRotateZ) (float rotateZ);struct ATweenTool* (*SetFadeTo) (float fadeTo);//--------------------------------------------------------------------------------------------------
// After SetValue then set TweenActionValue property for current context created
//--------------------------------------------------------------------------------------------------/*** After SetValue then SetRelative on new created TweenActiveValue*/struct ATweenTool* (*SetRelative) (bool isRelative);/*** After SetValue then SetEaseType on new created TweenActiveValue*/struct ATweenTool* (*SetEaseType) (TweenEaseType easeType);//--------------------------------------------------------------------------------------------------/*** Run actions all in current context, set action target if has actionValue* and use target be tweenId*/void (*RunActions) (void* target);/*** Run actions all in current context, action must set target* if has actionValue and return tweenId*/void* (*RunTargets) ();
};extern struct ATweenTool ATweenTool[1];我们需要一个链式调用的发起者，通常是一个单例对象。这里就是有ATweenTool充当。可以看到，几乎所有的函数都会直接返回 ATweenTool结构指针，这样就可以在函数调用完成的时候，链式的调用所属的其它函数形成链式调用。ATweenTool的方法有3大类。
第一类，生成一个Action，以SetAction开头的函数以及SetInterval函数，都会生成一个上下文Action对象。以后针对Action属性的设置函数，比如SetDuration，SetUserData等等，都会使用这个上下文的Action，可以看到这些函数并没有传入Action对象作为参数。当重新SetAction的时候，上下文对象就会重置。
第二类，生成一个ActionValue，以SetMove，SetScale等等这样的函数，都会生成一个上下文的ActionValue对象。以后针对ActionValue属性的设置函数，比如SetRelative等函数，都会使用这个上下文的ActionValue，可以看到这些函数并没有传入ActionValue作为参数。 当重新SetMove等时候，上下文对象就会重置。
第三类，RunActions和RunTargets两个函数，返回值不再是ATweenTool这样返回。意味着这是链式调用的终点。一旦调用Tween动画开始执行。
接下来，看看上下文是如何生成的。
#define action_length 30static Array(TweenAction*) actionArr[1] =
{(TweenAction*[action_length]) {},0
};static TweenAction* action = NULL;
static TweenActionValue* actionValue = NULL;就是简单的使用了一个static变量持有了Action数组。也就是说上下文Action的生成是有上限的。在执行tween动画执行之前，一共只能生成action_length个Action。那么，action和actionValue变量，就是记录了当前上下文的对象。随着新Action和ActionValue的设置，当前变量不断的被赋值。
#define CheckAction(tag) \ALogA(action != NULL, "ATweenTool " tag " TweenAction not created");#define CheckActionValue(tag) \ALogA(actionValue != NULL, "ATweenTool " tag " TweenActionValue invalid");static struct ATweenTool* SetAction()
{ALogA(actionArr->length <= action_length,"ATweenTool can not cache TweenActions = %d more than %d",actionArr->length,action_length);action = ATween->GetAction();actionValue = NULL;AArraySet(actionArr,actionArr->length++,action,TweenAction*);return ATweenTool;
}static inline struct ATweenTool* SetValue(TweenActionValueGetSet* valueGetSet, float value)
{CheckAction("SetValue");actionValue = ATween->AddTweenActionValue(action);actionValue->OnGet = valueGetSet->OnGet;actionValue->OnSet = valueGetSet->OnSet;actionValue->value = value;return ATweenTool;
}static struct ATweenTool* SetDuration(float duration)
{CheckAction("SetDuration");action->duration = duration;return ATweenTool;
}static struct ATweenTool* SetRelative(bool isRelative)
{CheckAction ("SetRelative");CheckActionValue("SetRelative");actionValue->isRelative = isRelative;return ATweenTool;
}static struct ATweenTool* SetEaseType(TweenEaseType easeType)
{CheckAction ("SetEaseType");CheckActionValue("SetEaseType");actionValue->easeType = easeType;return ATweenTool;
}static struct ATweenTool* SetInterval(float duration)
{SetAction();SetDuration(duration);return ATweenTool;
}//--------------------------------------------------------------------------------------------------static struct ATweenTool* SetActionMoveX(float moveX, float duration)
{SetAction();SetValue(ATweenActionValueGetSetImpl->moveX, moveX);SetDuration(duration);return ATweenTool;
}static struct ATweenTool* SetActionMoveY(float moveY, float duration)
{SetAction();SetValue(ATweenActionValueGetSetImpl->moveY, moveY);SetDuration(duration);return ATweenTool;
}static struct ATweenTool* SetActionMove(float moveX, float moveY, float duration, bool isRelative, TweenEaseType easeType)
{SetAction ();SetValue (ATweenActionValueGetSetImpl->moveX, moveX);SetRelative(isRelative);SetEaseType(easeType);SetValue (ATweenActionValueGetSetImpl->moveY, moveY);SetRelative(isRelative);SetEaseType(easeType);SetDuration(duration);return ATweenTool;
}static struct ATweenTool* SetActionScaleX(float scaleX, float duration)
{SetAction();SetValue(ATweenActionValueGetSetImpl->scaleX, scaleX);SetDuration(duration);return ATweenTool;
}static struct ATweenTool* SetActionScaleY(float scaleY, float duration)
{SetAction();SetValue(ATweenActionValueGetSetImpl->scaleY, scaleY);SetDuration(duration);return ATweenTool;
}static struct ATweenTool* SetActionScale(float scaleX, float scaleY, float duration, bool isRelative, TweenEaseType easeType)
{SetAction ();SetValue (ATweenActionValueGetSetImpl->scaleX, scaleX);SetRelative(isRelative);SetEaseType(easeType);SetValue (ATweenActionValueGetSetImpl->scaleY, scaleY);SetRelative(isRelative);SetEaseType(easeType);SetDuration(duration);return ATweenTool;
}static struct ATweenTool* SetActionRotateZ(float rotateZ, float duration)
{SetAction();SetValue(ATweenActionValueGetSetImpl->rotateZ, rotateZ);SetDuration(duration);return ATweenTool;
}static struct ATweenTool* SetActionFadeTo(float fadeTo, float duration)
{SetAction();SetValue(ATweenActionValueGetSetImpl->fadeTo, fadeTo);SetDuration(duration);return ATweenTool;
}//--------------------------------------------------------------------------------------------------static struct ATweenTool* SetUserData(void* userData)
{CheckAction("SetUserData");action->userData = userData;return ATweenTool;
}static struct ATweenTool* SetQueue(bool isQueue)
{CheckAction("SetQueue");action->isQueue = isQueue;return ATweenTool;
}static struct ATweenTool* SetOnComplete(TweenActionOnComplete OnComplete)
{CheckAction("SetOnComplete");action->OnComplete = OnComplete;return ATweenTool;
}static struct ATweenTool* SetTarget(void* target)
{CheckAction("SetTarget");action->target = target;return ATweenTool;
}static struct ATweenTool* GetAction(TweenAction** outActionPtr)
{CheckAction("GetAction");*outActionPtr = action;return ATweenTool;
}//--------------------------------------------------------------------------------------------------static struct ATweenTool* SetMoveX(float moveX)
{return SetValue(ATweenActionValueGetSetImpl->moveX, moveX);
}static struct ATweenTool* SetMoveY(float moveY)
{return SetValue(ATweenActionValueGetSetImpl->moveY, moveY);
}static struct ATweenTool* SetScaleX(float scaleX)
{return SetValue(ATweenActionValueGetSetImpl->scaleX, scaleX);
}static struct ATweenTool* SetScaleY(float scaleY)
{return SetValue(ATweenActionValueGetSetImpl->scaleY, scaleY);
}static struct ATweenTool* SetRotateZ(float rotateZ)
{return SetValue(ATweenActionValueGetSetImpl->rotateZ, rotateZ);
}static struct ATweenTool* SetFadeTo(float fadeTo)
{return SetValue(ATweenActionValueGetSetImpl->fadeTo, fadeTo);
}//--------------------------------------------------------------------------------------------------static void RunActions(void* target)
{ALogA(target, "RunActions, target must not NULL");for (int i = 0; i < actionArr->length; i++){TweenAction* action = AArrayGet(actionArr, i, TweenAction*);if (action->actionValueList->size > 0){action->target = target;}}ATween->RunActions(actionArr, &target);actionArr->length = 0;action = NULL;actionValue = NULL;
}static void* RunTargets()
{for (int i = 0; i < actionArr->length; i++){TweenAction* action = AArrayGet(actionArr, i, TweenAction*);if (action->actionValueList->size > 0){ALogA(action->target != NULL,"RunActions, the {%d} action has actionValue, so must set target",i);}}void* tweenId = NULL;ATween->RunActions(actionArr, &tweenId);actionArr->length = 0;action = NULL;actionValue = NULL;return tweenId;
}struct ATweenTool ATweenTool[1] =
{SetAction,SetInterval,SetActionMoveX,SetActionMoveY,SetActionMove,SetActionScaleX,SetActionScaleY,SetActionScale,SetActionRotateZ,SetActionFadeTo,SetDuration,SetUserData,SetQueue,SetOnComplete,SetTarget,GetAction,SetMoveX,SetMoveY,SetScaleX,SetScaleY,SetRotateZ,SetFadeTo,SetRelative,SetEaseType,RunActions,RunTargets,
};#undef action_length
#undef CheckAction
#undef CheckActionValue可以看到，所有链式调用的函数最后都会return ATweenTool结构。但执行tween动画以后，就会重置当前的上下文变量。那么，使用起来是一下这个样子的。
ATweenTool->SetActionMoveX(deltaX * 0.95f, enemy->hurtXTime)->SetEaseType (tween_ease_quad_in)->SetQueue (false)->SetOnComplete (AttackOnComplete)->SetUserData (enemy)->SetActionMoveY(0.03f, enemy->hurtYUpTime)->SetEaseType (tween_ease_quad_in)->SetActionMoveY(-0.03f, enemy->hurtYDownTime)->SetEaseType (tween_ease_quad_out)->RunActions (enemyDrawable);最后给出，额外辅助的结构。
typedef struct
{TweenActionValueOnGet OnGet;TweenActionValueOnSet OnSet;
}
TweenActionValueGetSet;struct ATweenActionValueGetSetImpl
{TweenActionValueGetSet moveX [1];TweenActionValueGetSet moveY [1];TweenActionValueGetSet scaleX [1];TweenActionValueGetSet scaleY [1];TweenActionValueGetSet rotateZ[1];TweenActionValueGetSet fadeTo [1];
};/*** Application must implement tween action value get set method*/
extern struct ATweenActionValueGetSetImpl ATweenActionValueGetSetImpl[1];
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