ActionController::UnknownFormat (SearchsController#index is missing a template for this request format and variant.

request.formats: ["text/html"]
request.variant: []

NOTE! For XHR/Ajax or API requests, this action would normally respond with 204 No Content: an empty white screen. Since you're loading it in a web browser, we assume that you expected to actually render a template, not nothing, so we're showing an error to be extra-clear. If you expect 204 No Content, carry on. That's what you'll get from an XHR or API request. Give it a shot.):

def index
#ViewのFormで取得したパラメータをモデルに渡す
    @projects = Search.search(params[:search])
end