How to format the url? - flutter

Question

I want to format url. Here is an example:
Input:
www.google.com
or
google.com
Output:
https://www.google.com/
I need to format the url because I'm using a validator function that needs to check if the text is a url. When I type www.google.com or google.com it says it's not a url because it requires https at the beginning of the text.
My code:
validator: (value) {
if (value == null) {
return null;
}
if (Uri.parse(value).host.isEmpty) {
return "Please type a valid url";
}
},
Feel free to leave a comment if you need more information.
How to format the url? I would appreciate any help. Thank you in advance!

Answer 1

I have added some more conditions to your validator function :
validator: (value) => {
if (value == null) {
return null;
}
if (!value.startsWith("https://")) {
value = "https://" + value;
}
if (!value.startsWith("https://www.") && !value.startsWith("https://")) {
value = "https://www." + value.substring(8);
}
if (Uri.parse(value).host.isEmpty) {
return "Please type a valid url";
}
}

Answer 2

I would first sanitize the URL with something like:
String ensureScheme(String url) {
var uri = Uri.tryParse(url);
if (uri == null || !uri.hasScheme) {
url = 'https://$url';
}
return url;
}
which would add an https URL scheme only if no scheme is already present, thereby avoiding mangling URLs that use other schemes (e.g. file:///some/path, mailto:user#example.com, ssh://user#host.example.com, tel:[phone]).
Additionally, note that your Uri.parse(value).host.isEmpty check is not quite correct:
Uri.parse will throw an exception if given unparsable input (e.g. ':'). You probably should be using Uri.tryParse instead.
An empty host does not necessarily imply an invalid URL. For example, all of the following would have an empty host:
file:///some/path
mailto:user#example.com
tel:[phone]
(But maybe that's okay if you don't care about such URLs.)