我认为这两种模式的类图显示了差异。

策略 在类中封装算法 图片链接

模板方法 将算法的精确步骤推迟到子类 链接到图片

You probably mean template method pattern. You are right, they serve very similar needs. I would say it is better to use template method in cases when you have a "template" algorithm having defined steps where subclasses override these steps to change some details. In case of strategy, you need to create an interface, and instead of inheritance you are using delegation. I would say it is a bit more powerful pattern and maybe better in accordance to DIP - dependency inversion principles. It is more powerful because you clearly define a new abstraction of strategy - a way of doing something, which does not apply to template method. So, if this abstraction makes sense - use it. However, using template method may give you simpler designs in simple cases, which is also important. Consider which words fit better: do you have a template algorithm? Or is the key thing here that you have an abstraction of strategy - new way of doing something

模板方法的例子:

Application.main()
{
Init();
Run();
Done();
}

这里你继承了application，并替换了init, run和done的操作。

策略的例子:

array.sort (IComparer<T> comparer)

在这里，当编写比较器时，您不继承数组。数组将比较算法委托给比较器。

模板模式用于特定操作具有某些可以根据其他变化的原语行为定义的不变行为。抽象类定义了不变行为，而实现类定义了相关方法。

在策略中，行为实现是独立的——每个实现类定义行为，它们之间没有共享代码。两者都是行为模式，因此被客户以大致相同的方式消费。通常策略只有一个公共方法——execute()方法，而模板可以定义一组公共方法以及一组支持的私有原语，这些原语必须由子类实现。

这两种模式可以很容易地结合使用。您可能有一个策略模式，其中几个实现属于使用模板模式实现的策略家族。

两者都非常相似，客户端代码以类似的方式使用它们。与上面最流行的答案不同，两者都允许在运行时选择算法。

The difference between the two is that while the strategy pattern allows different implementations to use completely different ways of the achieving the desired outcome, the template method pattern specifies an overarching algorithm (the "template" method) which is be used to achieve the result -- the only choice left to the specific implementations (sub-classes) are certain details of the said template method. This is done by having the the template method make call(s) to one or more abstract methods which are overridden (i.e. implemented) by the sub-classes, unlike the template method which itself is not abstract and not overridden by the sub-classes.

客户端代码使用抽象类类型的引用/指针调用模板方法，该引用/指针指向具体子类之一的实例，该实例可以在运行时确定，就像使用策略模式时一样。

在此设计模式的模板方法中，子类可以覆盖一个或多个算法步骤，以允许不同的行为，同时确保仍然遵循总体算法(Wiki)。

模式名Template方法的意思是它是什么。假设我们有一个方法calculatessomething()，我们想要创建这个方法的模板。此方法将在基类中声明为非虚方法。假设这个方法是这样的。

CalculateSomething(){
    int i = 0;
    i = Step1(i);
    i++;
    if (i> 10) i = 5;
    i = Step2(i);
    return i;

｝ Step1和Step2方法实现可以由派生类给出。

在策略模式中，基类没有提供实现(这就是为什么基类实际上是类图中的接口)。

经典的例子是排序。根据需要排序的对象数量，创建适当的算法类(merge, bubble, quick等)，并将整个算法封装在每个类中。

现在我们可以将排序实现为模板方法了吗?当然可以，但是您不会发现有太多/任何共性可以抽象出来并放置在基本实现中。因此，它违背了模板方法模式的目的。

我建议你读一下这篇文章。它解释了一个实际案例的差异。

引用自文章

"As one can see implementing classes also depend upon the template method class. This dependency causes to change the template method if one wants to change some of the steps of the algorithm. On the other side strategy completely encapsulates the algorithm. it gives the implementing classes to completely define an algorithm. Therefore if any change arrives one does need to change the code for previously written classes. This was the primary reason I choose strategy for designing up the classes. One feature of template method is that template method controls the algorithm. Which can be a good thing in other situation but in my problem this was restricting me to design the classes. On the other side strategy does not control the steps of an algorithm which enables me to add completely different conversion methods. Hence in my case strategy helps me for implementation. One drawback of strategy is that there is too much code redundancy and less code sharing. As it is obvious in the presented example of this article I have to repeat the same code in four classes again and again. Therefore it is hard to maintain because if the implementation of our system such as step 4 which is common to all is changed then I will have to update this in all 5 classes. On the other side, in template method, I can only change the superclass and the changes are reflected into the sub classes. Therefore template method gives a very low amount of redundancy and high amount of code sharing among the classes. Strategy also allows changing the algorithm at run-time. In template method one will have to re-initialize the object. This feature of strategy provide large amount of flexibility. From design point of view one has to prefer composition over inheritance. Therefore using strategy pattern also became the primary choice for development."