use params::{Map, Value};
pub fn validate_string(values: &Map, field: &str) -> Result<Option<Value>, String> {
match values.find(&[field]) {
Some(&Value::String(_)) => Ok(None),
None => {
// Allow empty values
Ok(None)
}
_ => {
Err(format!("The {} field must be a string.",
field.to_lowercase().replace("_", " ")))
}
}
}