如下列代码，在使用bufio包中的ReadString读取字符串之后，这个字符串无法进行类型转换，每次使用strconv.Atoi()函数返回值均为0。

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18

inputReader := bufio.NewReader(os.Stdin)
fmt.Println("Please input a number")
t, err := inputReader.ReadString('\n')
if err != nil {
    fmt.Println("can't read number!")
}
fmt.Println("the number is", t)
if num, ok := strconv.Atoi(t); ok != nil {
    fmt.Println("convert to int error", num)
}

//input
25
//output
Please input a number
the number is 25

convert to int error 0

因为这种写法其实经常遇到，之前编程的时候遇到这种情况没怎么注意，以为是算法问题，就换思路写了，直到这次只能用这种思路，才发现这里出现了问题。

Stackoverflow上相关的问题回答说这是因为ReadString读取字符串成功后会把'\n'一起加在字符串后面。查找包说明发现函数的原型和解释如下

1
2
3

func (b *Reader) ReadString(delim byte) (string, error)
/* ReadString reads until the first occurrence of delim in the input, returning a string containing the data up to and including the delimiter. If ReadString encounters an error before finding a delimiter, it returns the data read before the error and the error itself (often io.EOF). ReadString returns err != nil if and only if the returned data does not end in delim. For simple uses, a Scanner may be more convenient.
*/

这种情况给出的建议是利用strings.Trim…系列去除末尾添加的字符，比如，对上面的错误程序

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18

inputReader := bufio.NewReader(os.Stdin)
fmt.Println("Please input a number")
t, err := inputReader.ReadString('\n')
if err != nil {
    fmt.Println("can't read number!")
}
fmt.Println("the number is", t)
t = strings.TrimRight(t, "\n")
if num, ok := strconv.Atoi(t); ok == nil {
    fmt.Println("convert succeed", num)
}
//input 
25
//output
Please input a number
the number is 25

convert succeed 25