use params::{Map, Value};
pub fn validate_present(values: &Map, field: &[&str]) -> Result<Option<Value>, String> {
match values.find(field) {
Some(&Value::Null) |
None => {
Err(format!("The {} field must be present.",
field.last()
.unwrap()
.to_lowercase()
.replace("_", " ")))
}
_ => Ok(None),
}
}