Golang : Executing and evaluating nested loop in html template


Tags : golang html-template nested-loops range cant-evaluate-field

Alright, just a minor problem and putting the solution here on how to fix this problem for future reference. Basically, I need to loop two slices inside HTML template and somehow the inner loop will not be evaluated. Attempts to range over the inner slice will cause this error message:

template: editRenterPageBody:90:36: executing "editRenterPageBody" at <.currentlyRentedTheseProperties>: can't evaluate field currentlyRentedTheseProperties in type models.Property

and the code that caused this error message:

  {{range $forRent := .propertiesForRent}}
 {{ range $rented := .currentlyRentedTheseProperties}} <!-- can't evaluate field error! -->
 <option value="{{ $forRent.ID }}"
 {{ if (eq $forRent.ID $rented.ID )}}
 {{ print "selected" }}
 {{ end }}>{{ (wordlimiter $forRent.Name 5) }}</option>
 {{end}}
 {{end}}
  

after some investigation, the error message is caused by a missing '$`. We can read from the official documentation:

When execution begins, $ is set to the data argument passed to Execute, that is, to the starting value of dot.

Therefore, to fix this problem, we just add a $ in front of the inner loop.

  {{range $forRent := .propertiesForRent}}
 {{ range $rented := $.currentlyRentedTheseProperties}} <!-- need $. here instead of . -->
 <option value="{{ $forRent.ID }}"
 {{ if (eq $forRent.ID $rented.ID )}}
 {{ print "selected" }}
 {{ end }}>{{ (wordlimiter $forRent.Name 5) }}</option>
 {{end}}
 {{end}}
  

Hope this helps!

Happy coding!

Reference :

https://golang.org/pkg/text/template/#hdr-Variables

  See also : Golang : How to use if, eq and print properly in html template



Tags : golang html-template nested-loops range cant-evaluate-field

By Adam Ng

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