Often I'm facing lines like
result = 'Some text'
result += some_text_variable if some_text_variable.present?
And every time I want to replace that with something more accurate but I don't know how
Any ideas plz?
result += some_text_variable.to_s
It will work if some_text_variable is nil or empty string for example
But it always will concat empty string to original string
You can also use
result += some_text_variable.presence.to_s
It will work for all presence cases (for example for " " string)
You could "compact" and join an array, e.g.
['Some text', some_text_variable].select(&:present?).join
I realise this is a longhand form, just offering as an alternative to mutating strings.
This can look a bit nicer, if you have a large number of variables to munge together, or you want to join them in some other way e.g.
[
var_1,
var_2,
var_3,
var_4
].select(&:present?).join("\n")
Again, nothing gets mutated - which may or may not suit your coding style.
Related
I have user controller input like so (the length and # of items may change):
str = "['honda', 'toyota', 'lexus']"
I would like to convert this into an array, but I'm struggling to find the best way to do so. eval() does exactly what I need, but it is not very elegant and is dangerous in this case, since it's user controller input.
Another way is:
str[1..-2].split(',').collect { |car| car.strip.tr("'", '') }
=> ["honda", "toyota", "lexus"]
But this is also not very elegant. Any suggestions that are more 'Rubyish'?
You could use a regular expression:
# match (in a non-greedy way) characters up to a comma or `]`
# capture each word as a group, and don't capture `,` or `]`
str.scan(/'(.+?)'(?:,|\])/).flatten
Or JSON.parse (but accounting for the fact that single quotes are in fact technically not allowed in JSON):
JSON.parse( str.tr("'", '"') )
JSON.parse probably has a small edge over the regexp in terms of performance, but if you're expecting your users to do single quote escaping, then that tr is going to mess things up. In this case, I'd stick with the regexp.
The JSON.parse looks more correct, but here is another alternative:
str.split(/[[:punct:] ]+/).drop(1)
Is there a more Railsy way to do this (without explicit regex, perhaps?):
array_o_strings = ["some strings", "I'd like", "to parse"]
string = "like to parse"
re = Regexp.union(array_o_strings.map { |i| Regexp.new(i) })
string =~ re
Just pining for magical Rails methods.
There's really nothing wrong with using a regular expression here if that's your intent. It's generally more efficient to use one of those than to go through the trouble of comparing arrays.
It's worth noting you don't have to do that much work to get this:
re = Regexp.union(array)
That should handle automatically escaping those strings and compiling them into a singular regular expression. Test with strings containing * and ? to be sure.
One note to add on style is that the =~ operator is a hold-over from Perl. It's preferable to use string.match(re) to make it clear what's going on there.
How big is the array? It may be worth comparing the speed using a regex vs checking each element. If the array is sorted shortest to longest that would help when checking one by one as you're more likely to find a match first.
In any event, this is one way:
array_o_strings.any?{|e| string.index(e) }
I am using ruby on rails
I have
article.id = 509969989168Q000475601
I would like the output to be
article.id = 68Q000475601
basically want to get rid of all before it gets to 68Q
the numbers in front of the 68Q can be various length
is there a way to remove up to "68Q"
it will always be 68Q and Q is always the only Letter
is there a way to say remove all characters from 2 digits before "Q"
I'd use:
article.id[/68Q.*/]
Which will return everything from 68Q to the end of the string.
article.id.match(/68Q.+\z/)[0]
You can do this easily with the split method:
'68Q' + article.id.split('68Q')[1]
This splits the string into an array based on the delimiter you give it, then takes the second element of that array. For what it's worth though, #theTinMan's solution is far more elegant.
I know I have to use mysql_real_escape_string when running it in a query, for example:
$ProjectHasReservationQuery = ("
SELECT *
FROM reservelist rl
INNER JOIN project p on rl.projectid = p.projectid
WHERE rl.projectid = ". mysql_real_escape_string($record['projectid']) ."
AND restype = 'res'
");
But how about echoing it out, like:
query1 = mysql_query("SELECT * FROM users");
while ($record = mysql_fetch_array($query1 ))
{
echo "".stripslashes(mysql_real_escape_string($record['usersurname']))."";
// OR
echo "".$record['usersurname']."";
}
Which one is it? Personally I think echo "".$record['usersurname']."";, since this is coming FROM a query and not going INTO. But want to be 100% sure.
(I am aware about PDO and mysqli)
I know I have to use mysql_real_escape_string when running it in a query
Quite contrary, you should not use mysql_real_escape_string on a query like this.
It will do no good but leave you with false feeling of safety.
As you can say from the function name, it is used to escape strings, while you are adding a number. So, this function become useless, while your query still remains wide open for injection.
One have to use this function only to format quoted strings in the SQL query.
Thus you can conclude the answer from this rule: no, there is no point in using this function for output.
As for the protection, either treat your number as a string (by quoting and escaping it) or cast it using intval() function.
Or, the best choice, get rid of this manual formatting and start using placeholders to represent dynamical data in the query. it is not necessarily prepared statements - it could use the same escaping, but encapsulated in some placeholder handling function
I only found this related to what I am looking for: Split string by count of characters but it is not useful for what I mean.
I have a string variable, which is an ammount of 3 numbers (can be from 000 to 999). I need to separate each of the numbers (characters) and get them into a table.
I am programming for a game mod which uses lua, and it has some extra functions. If you could help me to make it using: http://wiki.multitheftauto.com/wiki/Split would be amazing, but any other way is ok too.
Thanks in advance
Corrected to what the OP wanted to ask:
To just split a 3-digit number in 3 numbers, that's even easier:
s='429'
c1,c2,c3=s:match('(%d)(%d)(%d)')
t={tonumber(c1),tonumber(c2),tonumber(c3)}
The answer to "How do I split a long string composed of 3 digit numbers":
This is trivial. You might take a look at the gmatch function in the reference manual:
s="123456789"
res={}
for num in s:gmatch('%d%d%d') do
res[#res+1]=tonumber(num)
end
or if you don't like looping:
res={}
s:gsub('%d%d%d',function(n)res[#res+1]=tonumber(n)end)
I was looking for something like this, but avoiding looping - and hopefully having it as one-liner. Eventually, I found this example from lua-users wiki: Split Join:
fields = {str:match((str:gsub("[^"..sep.."]*"..sep, "([^"..sep.."]*)"..sep)))}
... which is exactly the kind of syntax I'd like - one liner, returns a table - except, I don't really understand what is going on :/ Still, after some poking about, I managed to find the right syntax to split into characters with this idiom, which apparently is:
fields = { str:match( (str:gsub(".", "(.)")) ) }
I guess, what happens is that gsub basically puts parenthesis '(.)' around each character '.' - so that match would consider those as a separate match unit, and "extract" them as separate units as well... But I still don't get why is there extra pair of parenthesis around the str:gsub(".", "(.)") piece.
I tested this with Lua5.1:
str = "a - b - c"
fields = { str:match( (str:gsub(".", "(.)")) ) }
print(table_print(fields))
... where table_print is from lua-users wiki: Table Serialization; and this code prints:
"a"
" "
"-"
" "
"b"
" "
"-"
" "
"c"