Clean Code反案例：什么是不好的API

先来看两段代码：

CI.cs:

public BoundBlock3d meshOrthoBoundBlock(Matrix3d localToBound)
{
Matrix3d xfrm = localToBound * this.ChildToParentTransform;
return this.Child.meshOrthoBoundBlock(xfrm);
}

CD.cs
重构后的CI

public BoundBlock3d MeshOrthoBoundBlock()
{
return MeshOrthoBoundBlock(Matrix3d.Identity);
}

private BoundBlock3d MeshOrthoBoundBlock(Matrix3d localToBound)
{
BoundBlock3d bounds = new BoundBlock3d();
Matrix3d mtx = localToBound * this.Child.ScalingTransform;

foreach (CI childCI in this.Child.ReferencedCIs)
bounds.orthoExtend(MeshOrthoBoundBlock(mtx * childCI.ChildToParentTransform));

// Calculate self bounds
bounds.orthoExtend(activeBody.GetOrthoBoundingBlock(mtx));

return bounds;
}

CD.cs:
移去meshOrthoBoundBlock方法

大家可以看到为了避免Client传不必要的Matrix3d.Identity， 我在外面多包装了一层。现在对于外面来说会清净很多，没有混乱的API， Client应该不用头大了。