Go语言圣经–接口约定习题详解编程语言

package main 
 
import ( 
        "bufio" 
        "fmt" 
        "strings" 
) 
 
func main() { 
 
        var c WordsCounter 
        fmt.Fprintf(&c, "hello world 123") 
        fmt.Println(c) //输出 3 
} 
 
/* 
练习 7.1： 使用来自ByteCounter的思路，实现一个针对对单词和行数的计数器。你会发现bufio.ScanWords非常的有用。 
*/ 
type ByteCounter int  
 
func (c *ByteCounter) Write(p []byte) (int, error) { 
        *c += ByteCounter(len(p)) // convert int to ByteCounter 
        return len(p), nil  
} 
 
//定义类型 
type WordsCounter int  
 
//满足相同接口的类型 
func (w *WordsCounter) Write(p []byte) (int, error) { 
        //分隔字符串 
        s := strings.NewReader(string(p)) 
        bs := bufio.NewScanner(s) 
        bs.Split(bufio.ScanWords) 
        sum := 0 
        for bs.Scan() { 
                sum++ 
        }    
        *w = WordsCounter(sum) 
        return sum, nil  
}