构造奇怪的行为

Question

I just started to play with Go-lang and come across a Strange behavior of it Structs. I have a Struct A and another Struct B, in Struct B one key defined as []A the problem is when assigning the value of new instance type of B as elements of A it throw error despite the types are same. Any help will be greatly appreciated Below here I am pasting the minimal code which cause error

package main

import (
    "fmt"
    "math"
    "github.com/shirou/gopsutil/disk"
    "strconv"
)

func main() {

    /************ disk details goes here ************/
    diskPartitions, err := disk.Partitions(true)
    dealwithErr(err)
    fmt.Println(diskPartitions)

    type PARTITIONLIST []PARTITION
    var partitionsList PARTITIONLIST

    for partitionIndex, partition := range diskPartitions {
        partitionStat, err := disk.Usage(partition.Mountpoint)
        dealwithErr(err)

        var partitionDetails = PARTITION{
            "PARTITION",
            partitionIndex,
            partition.Mountpoint,
            "" + fmt.Sprint(partitionStat.Total) + " and " + bytesToSize(partitionStat.Total),
            "" + fmt.Sprint(partitionStat.Used) + " and " + bytesToSize(partitionStat.Used),
            "" + fmt.Sprint(partitionStat.Free) + " and " + bytesToSize(partitionStat.Free),
            "" + fmt.Sprint(partitionStat.UsedPercent) + "and " + strconv.FormatFloat(partitionStat.UsedPercent, 'f', 2, 64),
        }

        partitionsList = append(partitionsList, partitionDetails)
    }

    //till here working fine
    fmt.Println(partitionsList)

    //THE BELOW TWO LINES ERROR IS THE ACTUAL ERROR I AM ASKING
    var partitionDetails = PARTITIONS{
        "partitions",
        partitionsList
    }



    dealwithErr(err)
}

/************ all struct goes here ************/

type PARTITION struct {
    Name                   string
    Partition_index        int
    Partition              string
    Total_space_in_bytes   string
    Used_space_in_bytes    string
    Free_space_in_bytes    string
    Percentage_space_usage string
}

type PARTITIONLIST []PARTITION

type PARTITIONS struct {
    Name                string
    List                []PARTITIONS
}

/************ helper functions goes below here ************/
func bytesToSize(bytes uint64) string {
    sizes := []string{"Bytes", "KB", "MB", "GB", "TB"}
    if bytes == 0 {
        return fmt.Sprint(float64(0), "bytes")
    } else {
        var bytes1 = float64(bytes)
        var i = math.Floor(math.Log(bytes1) / math.Log(1024))
        var count = bytes1 / math.Pow(1024, i)
        var j = int(i)
        var val = fmt.Sprintf("%.1f", count)
        return fmt.Sprint(val, sizes[j])
    }
}

func dealwithErr(err error) {
    if err != nil {
        fmt.Println(err)
    }
}

EDIT: that error am getting on run time

unexpected newline, expecting comma or }

and that warning editor show on IDE

Cannot use partitionsList (type PARTITIONSLIST) as type []PARTITIONS

Answer 1

As the error clearly says:

Cannot use partitionsList (type PARTITIONSLIST) as type []PARTITIONS

You have type mismatch problem in the struct. Since PARTITIONSLIST is not qualy to []PARTITIONS. So if you create variable of both types they are different.

type PARTITIONLIST []PARTITION

type PARTITIONS struct {
    Name                string
    List                []PARTITIONS // here the list is slice of Partitions.
}

While when you are creating a slice of PARTITIONLIST type.

var partitionsList PARTITIONLIST // this is a variable of PARTITIONLIST type which is not equal to `[]PARTITIONS`

This is because golang is strictly typed language. So even if the underlying type of both values are similar. The are still different. To be more simple Try this example:

package main

import "fmt"

type MyInt int

func main() {
    var a int = 2
    var b MyInt = 2
    fmt.Println(a==b)
}

Output:

invalid operation: a == b (mismatched types int and MyInt)

Playground Example

So you need to create a slice of []PARTITIONS as:

var partitionsList `[]PARTITIONS`

or you can create both variables of PARTITIONLIST type to make them similar.

Another error:

unexpected newline, expecting comma or }

is because you need to pass , after last field if you are using it in new line as:

var partitionDetails = PARTITIONS{
    "partitions",
    partitionsList, // pass comma here in your code.
}

Full working example :

package main

import (
    "fmt"
    "math"
    "strconv"

    "github.com/shirou/gopsutil/disk"
)

func main() {

    /************ disk details goes here ************/
    diskPartitions, err := disk.Partitions(true)
    dealwithErr(err)
    fmt.Println(diskPartitions)

    var partitionsList PARTITIONLIST

    for partitionIndex, partition := range diskPartitions {
        partitionStat, err := disk.Usage(partition.Mountpoint)
        dealwithErr(err)

        var partitionDetails = PARTITION{
            "PARTITION",
            partitionIndex,
            partition.Mountpoint,
            "" + fmt.Sprint(partitionStat.Total) + " and " + bytesToSize(partitionStat.Total),
            "" + fmt.Sprint(partitionStat.Used) + " and " + bytesToSize(partitionStat.Used),
            "" + fmt.Sprint(partitionStat.Free) + " and " + bytesToSize(partitionStat.Free),
            "" + fmt.Sprint(partitionStat.UsedPercent) + "and " + strconv.FormatFloat(partitionStat.UsedPercent, 'f', 2, 64),
        }

        partitionsList = append(partitionsList, partitionDetails)
    }

    //till here working fine
    fmt.Println(partitionsList)

    //THE BELOW TWO LINES ERROR IS THE ACTUAL ERROR I AM ASKING
    var partitionDetails = PARTITIONS{
        "partitions",
        partitionsList,
    }

    fmt.Println(partitionDetails)

    dealwithErr(err)
}

/************ all struct goes here ************/

type PARTITION struct {
    Name                   string
    Partition_index        int
    Partition              string
    Total_space_in_bytes   string
    Used_space_in_bytes    string
    Free_space_in_bytes    string
    Percentage_space_usage string
}

type PARTITIONLIST []PARTITION

type PARTITIONS struct {
    Name string
    List PARTITIONLIST
}

/************ helper functions goes below here ************/
func bytesToSize(bytes uint64) string {
    sizes := []string{"Bytes", "KB", "MB", "GB", "TB"}
    if bytes == 0 {
        return fmt.Sprint(float64(0), "bytes")
    } else {
        var bytes1 = float64(bytes)
        var i = math.Floor(math.Log(bytes1) / math.Log(1024))
        var count = bytes1 / math.Pow(1024, i)
        var j = int(i)
        var val = fmt.Sprintf("%.1f", count)
        return fmt.Sprint(val, sizes[j])
    }
}

func dealwithErr(err error) {
    if err != nil {
        fmt.Println(err)
    }
}

Playground example