Question

What I have
I have templates that are stored in a database, and JSON data that gets converted into a dictionary in C#.

Example: 

Template: “Hi {FirstName}”

Data: “{FirstName: ‘Jack’}”

This works easily with one level of data by using a regular expression to pull out anything within {} in the template.

What I want
I would like to be able to go deeper in the JSON than the first layer.

Example:

Template: “Hi {Name: {First}}”

Data: “{Name: {First: ‘Jack’, Last: ‘Smith’}}”

What approach should I be taking? (and some guidance on where to start with your pick)

1. A regular expression
2. Not use JSON in the template (in favor of xslt or something similar)
3. Something else

I’d also like to be able to loop through data in the template, but I have no idea at all where to start with that one!

Thanks heaps

Answer 1

Here is how I would do it:

Change your template to this format Hi {Name.First}

Now create a JavaScriptSerializer to convert JSON in Dictionary<string, object>

JavaScriptSerializer jss = new JavaScriptSerializer();
dynamic d = jss.Deserialize(data, typeof(object));

Now the variable d has the values of your JSON in a dictionary.

Having that you can run your template against a regex to replace {X.Y.Z.N} with the keys of the dictionary, recursively.

Full Example:

public void Test()
{
    // Your template is simpler
    string template = "Hi {Name.First}";

    // some JSON
    string data = @"{""Name"":{""First"":""Jack"",""Last"":""Smith""}}";

    JavaScriptSerializer jss = new JavaScriptSerializer();

    // now `d` contains all the values you need, in a dictionary
    dynamic d = jss.Deserialize(data, typeof(object));

    // running your template against a regex to
    // extract the tokens that need to be replaced
    var result = Regex.Replace(template, @"{?{([^}]+)}?}", (m) =>
        {
            // Skip escape values (ex: {{escaped value}} )
            if (m.Value.StartsWith("{{"))
                return m.Value;

            // split the token by `.` to run against the dictionary
            var pieces = m.Groups[1].Value.Split('.');
            dynamic value = d;

            // go after all the pieces, recursively going inside
            // ex: "Name.First"

            // Step 1 (value = value["Name"])
            //    value = new Dictionary<string, object>
            //    {
            //        { "First": "Jack" }, { "Last": "Smith" }
            //    };

            // Step 2 (value = value["First"])
            //    value = "Jack"

            foreach (var piece in pieces)
            {
                value = value[piece]; // go inside each time
            }

            return value;
        });
}

I didn’t handle exceptions (e.g. the value couldn’t be found), you can handle this case and return the matched value if it wasn’t found. m.Value for the raw value or m.Groups[1].Value for the string between {}.