go - 在 Go 中实现一个接口(interface)

Question

我的项目组织如下

github.com/achanda/poke
├── cmd
│   └── poke.go
├── scanner.go
├── txt_scanner.go
└── types.go

文件如下

# cat scanner.go
package poke

type Scanner interface {
    Scan() *ScanResult
}

# cat txt_scanner.go
package poke

type txtScanner struct {
    txt string
}

func newTxtScanner(host string) Scanner {
    return txtScanner{txt}
}

func (tcpcs txtScanner) Scan() *ScanResult {
    // do stuff
    return &result
}

现在我正尝试在我的主包(在 poke.go 中)中这样调用它

package main

import "github.com/achanda/poke"

func main() {
    var sr poke.Scanner
    sr = poke.txtScanner{txt}
    sr.Scan()
}

运行失败

# command-line-arguments
./poke.go:111: cannot refer to unexported name poke.txtScanner
./poke.go:111: undefined: portscan.txtScanner

我做错了什么？

Answer 1

您需要访问包外的类型或字段，因此您应该使用首字母大写导出它们:

首先你应该用第一个大写字母定义你的txtScanner和txt string，否则你也会看到这个错误:

.\poke.go:8: implicit assignment of unexported field 'txt' in poke.TxtScanner literal

像这样:

type TxtScanner struct {
    Txt string
}

另请参阅此工作示例代码中的 newTxtScanner(host string) 函数:
捅Go:

package main

import "github.com/achanda/poke"

func main() {
    s := "test"
    var sr poke.Scanner
    sr = poke.TxtScanner{s}
    sr.Scan()
}

txt_scanner.go:

package poke

type TxtScanner struct {
    Txt string
}

func newTxtScanner(host string) Scanner {
    return TxtScanner{host}
}

func (tcpcs TxtScanner) Scan() *ScanResult {
    // do stuff
    result := ScanResult{}
    return &result
}

类型.go:

package poke

type ScanResult struct {
}

扫描仪.go:

package poke

type Scanner interface {
    Scan() *ScanResult
}