how to get a String with String.Format to execute?

Question

I have a little chunk of code (see below) that is returning the string:

string.Format("{0}----{1}",3,"test 2");

so how do I get this to actually "Execute"? To run and do the format/replacement of {0} and {1}?

My Code snippet:

StringBuilder sb = new StringBuilder();
sb.Append("{0}----{1}\",");
sb.AppendFormat(ReturnParamValue(siDTO, "siDTO.SuggestionItemID,siDTO.Title"));
string sbStr = "=string.Format(\""+sb.ToString()+");";

yes, ReturnParamValue gives the actually value of the DTO.

Anyways, I've taken a look at the following (but it doesn't say how to execute it: http://stackoverflow.com/questions/3319896/how-to-get-string-format-not-to-parse-0

Maybe, I just should put my code snippet in a method. But, what then?

Answer 1

I don't think you can execute it. Java is not really a interpreted language.

You may make use of scripting languages (which can even embed in your Java app as I know, start from JDK6) for such purpose, like Groovy

Answer 2

You could use RegEx to parse the three parameters out of the string, and then pass them to a real, actual string.Format method :-)

Answer 3

It looks like what you want is something like this:

string sbStr = string.Format("{0}----{1}", siDTO.SuggestionItemID, siDTO.Title);

Answer 4

Why are you including String.Format in the string itself?

If you're looking for a generic "let me evaluate this arbitrary expression I've built up in a string" then there isn't a simple answer.

If, instead, you're looking at how to provide the parameters to the string from a function call, then you've got yourself all twisted up and working too hard.

Try something like this, based on your original code:

string result
    = string.Format(
        "{0}----{1}",
        ReturnParamValue(siDTO, "siDTO.SuggestionItemID,siDTO.Title"));

Though, this won't entirely work since your original code seems to be only providing a single value, and you have two values in your format string - the {0} will be replaced with the value from your function, and {1} left unchanged.

What output are you expecting?

Does your ReturnParamValue() function try to return both the label and the value in a single string? If it does, and if they're comma separated, then you could try this:

var value = ReturnParamValue(siDTO, "siDTO.SuggestionItemID,siDTO.Title"));
var pieces = string.Split(',');
string result
    = string.Format( "{0}----{1}", pieces[0], pieces[1]);

Though this is seriously working too hard if ReturnParamValue() is a method you control.

Update Fri 6 August

Check out the declaration for string.Format() as shown on MSDN:

public static string Format(
    string format,
    params Object[] args
)

Unlike the special casing you might have seen in C for printf(), there's nothing special or unusual about the way string.Format() handles multiple parameters. The key is the params keyword, which asks the compiler to provide a little "syntactic sugar" where it combines the parameters into an array for you.

Key here is that the wrapping doesn't happen if you're already passing a single object[] - so if you wanted to, you could do something like this:

object[] parameters 
    = ReturnParamValues(siDTO, "siDTO.SuggestionItemID,siDTO.Title");
string result
    = string.Format("{0}----{1}----{2}", parameters);

Though, if I saw something like this in any codebase I maintained, I'd be treating it as a code-smell and looking for a better way to solve the problem.

Just because it's possible doesn't mean it's advisable. YMMV, of course.

Answer 5

Maybe i didn't understand your question completely, but it sounds like you need to format a format-string. If that's true you could maybe try something like this:

int width = 5;
string format = String.Format("{{0,{0}}}----{{1,{0}}}", width);
string result = String.Format(format, "ab", "cd");

So the trick is simply to escape the { or } by using a double {{ or }}.