How to compare the length of a list in html/template in golang?

问题

I am trying to compare the length of a list in golang html/template. But it is loading forever in html.

{{ $length := len .SearchData }} {{ if eq $length "0" }}
    Sorry. No matching results found
{{ end }}

Could anyone help me with this?

回答1:

From documentation,

{{if pipeline}} T1 {{end}}: If the value of the pipeline is empty, no output is generated; otherwise, T1 is executed. The empty values are false, 0, any nil pointer or interface value, and any array, slice, map, or string of length zero. Dot is unaffected.

So if you want to check if the .SearchData slice/array/map is empty just use,

{{if not .SearchData}} Nothing to show {{end}}

Even your code runs fine if string "0" is replaced by int 0

{{ $length := len .SearchData }} {{ if eq $length 0 }}
    Sorry. No matching results found
{{ end }}

http://play.golang.org/p/Q44qyRbKRB

回答2:

A shorter version

{{ if eq (len .SearchData) 0 }}
    Sorry. No matching results found
{{ end }}

回答3:

There is {{ else }} for {{ range }} Works well for maps as well https://play.golang.org/p/7xJ1LXL2u09:

{{range $item := . }}    
    <span>{{ $item }}</span>
{{ else }}
    <span>Sorry no rows here</span>
{{ end }}

来源：https://stackoverflow.com/questions/35967109/how-to-compare-the-length-of-a-list-in-html-template-in-golang