英文:
Parameter to Go custom template function
问题
请看 https://play.golang.org/p/EbWA15toVa9
我在其中：
- 在第25行定义了
func iterate(count int) []int - 在第15行调用了
iterate 5
这一切都没问题，但是，当我在第20行调用 iterate (printf "%d" 3) 时，我得到了以下错误：
template: t:12:39: 执行“t”时出错 <3>: 错误的值类型；期望 int，得到 string
难道不应该先执行 (printf "%d" 3)，然后在传递给 iterate 时变成 iterate 3 吗？为什么会出现上述错误？
完整的代码如下：
package main
import (
"log"
"os"
"text/template"
)
var x = `{{define "t1"}}
{{- index . 0}} {{index . 1}} {{index . 2}} {{index . 3}}
{{end -}}
hello, {{template "t1" args . 543 false 0.1234}}
{{- range $val := iterate 5 }}
{{ $val }}
{{- end }}
{{ (printf "%d" 3) }}
{{- range $val := iterate (printf "%d" 3) }}
{{ $val }}
{{- end }}
`
func iterate(count int) []int {
var i int
var Items []int
for i = 0; i < (count); i++ {
Items = append(Items, i)
}
return Items
}
func args(vs ...interface{}) []interface{} { return vs }
func main() {
t := template.Must(template.New("t").Funcs(template.FuncMap{"args": args, "iterate": iterate}).Parse(x))
err := t.Execute(os.Stdout, "foobar")
if err != nil {
log.Fatal(err)
}
}
英文:
Please take a look at https://play.golang.org/p/EbWA15toVa9
in which I
- define
func iterate(count int) []inton line 25 - call it with
iterate 5on line 15
That's all OK, but, when call it with iterate (printf "%d" 3) on line 20, I got the error of:
template: t:12:39: executing "t" at <3>: wrong type for value; expected int; got string
Wouldn't the (printf "%d" 3) get executed first and when passed to iterate, it'll become iterate 3? Why the above error instead?
Full code enclosed:
package main
import (
"log"
"os"
"text/template"
)
var x = `{{define "t1"}}
{{- index . 0}} {{index . 1}} {{index . 2}} {{index . 3}}
{{end -}}
hello, {{template "t1" args . 543 false 0.1234}}
{{- range $val := iterate 5 }}
{{ $val }}
{{- end }}
{{ (printf "%d" 3) }}
{{- range $val := iterate (printf "%d" 3) }}
{{ $val }}
{{- end }}
`
func iterate(count int) []int {
var i int
var Items []int
for i = 0; i < (count); i++ {
Items = append(Items, i)
}
return Items
}
func args(vs ...interface{}) []interface{} { return vs }
func main() {
t := template.Must(template.New("t").Funcs(template.FuncMap{"args": args, "iterate": iterate}).Parse(x))
err := t.Execute(os.Stdout, "foobar")
if err != nil {
log.Fatal(err)
}
}
答案1
得分: 3
你是正确的，printf "%d" 3会首先被评估。问题似乎是printf "%d" 3生成了一个字符串，但是你的iterate函数的参数类型是int。这个字符串不会被转换。
英文:
You are correct that the printf “%d” 3 gets evaluated first. The problem seems to be that printf “%d” 3 produces a string, but your iterate function has an argument of type int. The string will not be converted.
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