In software development, when the overall structure of some business logic is the same, but the implementation of some steps needs to be flexibly adjusted,Template Method PatternIt provides an elegant solution. It makes the code more flexible and easy to extend by defining a general framework of the algorithm and leaving some of the implementation to subclasses.

This article will introduce in detail the concept of the template method pattern, the difference from other patterns, the problems it solves, implementation examples in Golang, and its application and precautions in actual development.

What is Template Method Pattern?

Template Method Patternis aBehavioral design patterns, which defines an algorithmGeneral framework, and allows subclasses to redefine the implementation of certain steps without changing the overall structure of the algorithm.Template method in base classTo control the execution flow of the algorithm, the specific steps areSubclass to rewrite.

Components of the Template Method pattern

1. Abstract Class: A general framework for defining algorithms, including template methods and optional hook methods.
2. Template Method: Defines the execution steps of the algorithm. Some steps are implemented by abstract classes, and some steps are implemented by subclasses.
3. Concrete Class: Implements certain steps defined in the abstract class.

Differences between Template Method Pattern and Other Patterns

1. Strategy Pattern

• Target: The strategy pattern defines a series of algorithms and selects one to execute at runtime.
• the difference: The strategy pattern allows switching between different strategies, while the template method pattern fixes the overall structure of the algorithm and only allows certain steps to be changed.

2. Factory Method Pattern

• Target: The factory method pattern creates objects by defining an interface, and the subclass decides which class to instantiate.
• the difference: The factory method pattern focuses on the creation of objects, and the template method pattern focuses on the structuring of execution logic.

3. Command Pattern

• Target: The command pattern encapsulates requests as objects, thereby realizing parameterization, queuing, and cancellation of requests.
• the difference: The command pattern encapsulates the request operation, while the template method pattern encapsulates the algorithm flow.

What problem does the Template Method pattern solve?

1. Code Reuse: Extract the common parts of the algorithm into a base class to avoid code duplication.
2. Improve scalability: Parts of the algorithm can be easily extended and modified by inheriting and overriding steps.
3. Algorithm flow control: The template method ensures the execution order of the algorithm and prevents subclasses from arbitrarily changing the process.
4. Decoupling and the Open-Closed Principle: Subclasses only need to implement the necessary steps without having to worry about the overall logic of the algorithm.

Application scenarios of template method pattern

1. Data processing flow: When processing data, the preprocessing, processing, and post-processing steps can be abstracted into template methods.
2. Game Development: In game development, different types of player characters can implement common operation logic and customize some behaviors through template methods.
3. File Parser: When parsing files of different formats, the steps for reading the files are the same, but the specific parsing logic can be implemented through subclasses.
4. Web Request Processing: In the Web framework, different request processing processes (such as authentication, verification, and response) can be implemented through the template method.

Template method pattern implementation in Golang

Since there is no concept of class and inheritance in Golang, we can useInterfaces and Combinationsway to implement the template method pattern.

Example: Beverage Making System

We are implementing a beverage making system. Different beverages (such as tea and coffee) have some common steps, but also have their own special steps. We will implement these logics through the Template Method pattern.

1. Define the template interface

package main import "fmt" // Beverage interface: defines a process template for making beverages type Beverage interface { BoilWater() // Boil water Brew() // Brew (subclass implementation) PourInCup() // Pour into the cup AddCondiments() // Add seasoning (subclass implementation) MakeBeverage() // Template method }

2. Implementing Template Methods

// MakeBeverage implements a general production process (template method) func MakeBeverage(b Beverage) { b.BoilWater() b.Brew() b.PourInCup() b.AddCondiments() }

3. Implement specific beverages (coffee and tea)

// Tea struct: specific beverage - tea type Tea struct{} func (t *Tea) BoilWater() { fmt.Println("Boiling water for tea.") } func (t *Tea) Brew() { fmt.Println("Steeping the tea.") } func (t *Tea) PourInCup() { fmt.Println("Pouring tea into cup.") } func (t *Tea) AddCondiments() { fmt.Println("Adding lemon.") } // Coffee struct: specific beverage - coffee type Coffee struct{} func (c *Coffee) BoilWater() { fmt.Println("Boiling water for coffee.") } func (c *Coffee) Brew() { fmt.Println("Dripping coffee through filter.") } func (c *Coffee) PourInCup() { fmt.Println("Pouring coffee into cup.") } func (c *Coffee) AddCondiments() { fmt.Println("Adding sugar and milk.") }

4. Make drinks using the template method

func main() { fmt.Println("Making tea:") MakeBeverage(&Tea{}) fmt.Println("\nMaking coffee:") MakeBeverage(&Coffee{}) }

Output

Making tea: Boiling water for tea. Steeping the tea. Pouring tea into cup. Adding lemon. Making coffee: Boiling water for coffee. Dripping coffee through filter. Pouring coffee into cup. Adding sugar and milk.

Code Analysis

1. Beverage Interface: Defines the template method and steps for making beverages, and specific beverages need to implement these steps.
2. MakeBeverage function: This is the template method, which controls the overall process of making a drink.
3. Tea and Coffee structures: Achieved Beverage The methods in the interface define their own special steps.
4. main function: Shows how to make different drinks using a template approach.

Application in actual development

1. Web Request Lifecycle: In a web framework, request processing usually includes authentication, logging, processing requests, and returning responses. The Template Method pattern can be used to define these steps and allow developers to customize the logic of certain steps.
2. Algorithm template: In machine learning or data processing systems, data preprocessing, model training, and evaluation can be encapsulated as template methods, allowing users to customize some of the steps.
3. Character Behavior in Game Development： Different types of characters (such as warriors and mages) may share the same combat logic, but the specific skill release methods are different. In this case, the template method pattern can be used.

Notes on using the Template Method pattern

1. Avoid abuse of inheritance: Although the template method pattern encourages the rewriting of some steps through inheritance, in Golang, we should try toCombinations and interfacesImplementation, avoid overly complex class hierarchies.
2. Extensibility of the Template Method: When designing a template method, you need to ensure that each step in the process can be overridden by subclasses to enhance the flexibility of the system.
3. Keep template methods simple: Template methods should be kept as simple as possible, only responsible for controlling the process, and should not contain too much business logic.

Template Method Pattern vs. Strategy Pattern

Summarize

The Template Method pattern is a very useful design pattern that allows subclasses to rewrite some steps without changing the overall structure by defining a common framework for the algorithm. In Golang, we can do this byInterfaces and CombinationsThe template method pattern is implemented in this way. In actual development, the template method pattern is suitable for scenarios such as Web request processing, algorithm templates, and data processing.

Reference Links

• Design Patterns - Template Method Pattern
• Golang Design Patterns