Rails 5 中 redirect_to :back
在 Rails 5 中用 redirect_back(fallback_location: root_path) 来代替原先的 redirect_to :back
因为 redirect_to :back 中 :back 即等于 request.env["HTTP_REFERER"]
但在网络的环境中请求来源是多样的，举一个例子
当你直接复制链接到地址栏里访问时，若页面中使用了 redirect_to :back ，那么此时就会出错。
而最新的修订中，则指明了当 request.env["HTTP_REFERER"] 不存在时，返回哪一个页面，即 fallback_location 。
具体见：Add “redirect_back” and deprecate “redirect_to :back”
# Redirects the browser to the page that issued the request (the referrer)
# if possible, otherwise redirects to the provided default fallback
# location.
#
# The referrer information is pulled from the HTTP `Referer` (sic) header on
# the request. This is an optional header and its presence on the request is
# subject to browser security settings and user preferences. If the request
# is missing this header, the <tt>fallback_location</tt> will be used.
#
# redirect_back fallback_location: { action: "show", id: 5 }
# redirect_back fallback_location: @post
# redirect_back fallback_location: "http://www.rubyonrails.org"
# redirect_back fallback_location: "/images/screenshot.jpg"
# redirect_back fallback_location: posts_url
# redirect_back fallback_location: proc { edit_post_url(@post) }
#
# All options that can be passed to <tt>redirect_to</tt> are accepted as
# options and the behavior is identical.
def redirect_back(fallback_location:, **args)
if referer = request.headers["Referer"]
redirect_to referer, **args
else
redirect_to fallback_location, **args
end
end
<%= link_to "Back", :back %>
<%= link_to "back", request.referer.present? ? request.referer : root_path %>
<%= link_to url_for(request.env["HTTP_REFERER"].present? ? request.env["HTTP_REFERER"] : root_path) %>
<%= link_to url_for(request.env["HTTP_REFERER"] || root_path) %>