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Documentation: func String() description in "Effective Go" is wrong #1796

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gopherbot opened this issue May 11, 2011 · 3 comments
Closed

Documentation: func String() description in "Effective Go" is wrong #1796

gopherbot opened this issue May 11, 2011 · 3 comments
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@gopherbot
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by christopher.helck:

Document "Effective Go" under the Printing section shows how to write String()
function for object T:

func (t *T) String() string {
    return fmt.Sprintf("%d/%g/%q", t.a, t.b, t.c)
}
fmt.Printf("%v\n", t)


This is incorrect, the function should not take a pointer, instead it should be written
as:

func (t T) String() string {
    return fmt.Sprintf("%d/%g/%q", t.a, t.b, t.c)
}
fmt.Printf("%v\n", t)


The tutorial has the same issue, but the specification is correct.

I checked to see how String() method is written in packages. See
http://golang.org/src/pkg/image/geom.go?s=1791:1825#L69 for an example.

As a beginner I found this hard to debug.
@rsc
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rsc commented May 11, 2011

Comment 1:

Haven't looked to confirm this.  Might or might not be true.

Owner changed to @robpike.

Status changed to Accepted.

@gopherbot
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Comment 2 by christopher.helck:

Here is a test. Should fail with Pointer type
package main
import (
    "fmt"
    "testing"
)
type Foo struct {
    a, b int
}
func (foo *Foo) String() string {
    return "FOO"
}
func TestString1(t *testing.T) {
    f := Foo{1,2}
    s := f.String()
    if s != "FOO" {
        t.Error("f.String() returned: " + s)
    }
}
func TestString2(t *testing.T) {
    f := Foo{1,2}
    s := fmt.Sprintf("Foo: %v", f)
    if s != "Foo: FOO" {
        t.Error("f.String() returned: " + s)
    }
}

@robpike
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robpike commented May 11, 2011

Comment 3:

This issue was closed by revision 89c59bc.

Status changed to Fixed.

@golang golang locked and limited conversation to collaborators Jun 24, 2016
@rsc rsc unassigned robpike Jun 22, 2022
This issue was closed.
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@rsc @robpike @gopherbot