diff --git a/src/getopt.rs b/src/getopt.rs
index f7668c6..b95108c 100644
--- a/src/getopt.rs
+++ b/src/getopt.rs
@@ -31,31 +31,24 @@ pub enum OptError {
 
 // Function signature
 pub trait GetOpt {
-	fn getopt(
-		argv: Vec<String>,
-		optstring: &str
-	) -> Option<Result<Opt, OptError>>;
+	fn getopt(&self, optstring: &str) -> Option<Result<Opt, OptError>>;
 }
 
 impl GetOpt for Vec<String> {
-	fn getopt(
-		argv: Vec<String>,
-		optstring: &str
-	) -> Option<Result<Opt, OptError>> {
+	fn getopt(&self, optstring: &str) -> Option<Result<Opt, OptError>> {
+		let argv = self
+			.iter()
+			.cloned()
+			.map(CString::new)
+			.map(Result::unwrap)
+			.map(|x| x.as_ptr() as c_char)
+			.collect::<Vec<c_char>>()
+			.as_ptr() as *const *mut c_char;
+		let opts = CString::new(optstring).unwrap().into_raw();
+		let len = self.len() as c_int;
+
 		unsafe {
-			let args = argv
-				.iter()
-				.cloned()
-				.map(CString::new)
-				.map(Result::unwrap)
-				.map(|x| x.as_ptr() as c_char)
-				.collect::<Vec<c_char>>()
-				.as_ptr() as *const *mut c_char;
-
-			let len = argv.len() as c_int;
-			let opts = CString::new(optstring).unwrap().into_raw();
-
-			let a = match getopt(len, args, opts) {
+			let a = match getopt(len, argv, opts) {
 				/* From getopt(3p):
 				 *
 				 * The getopt() function shall return the next option character