1 files changed, 40 insertions, 0 deletions
diff --git a/clap/examples/10_default_values.rs b/clap/examples/10_default_values.rs
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+++ b/clap/examples/10_default_values.rs
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+extern crate clap;
+
+use clap::{App, Arg};
+
+fn main() {
+    // There are two ways in which to get a default value, one is to use claps Arg::default_value
+    // method, and the other is to use Rust's built in Option::unwrap_or method.
+    //
+    // I'll demo both here.
+    //
+    // First, we'll use clap's Arg::default_value with an "INPUT" file.
+    let matches = App::new("myapp").about("does awesome things")
+                        .arg(Arg::with_name("INPUT")
+                                .help("The input file to use") // Note, we don't need to specify
+                                                               // anything like, "Defaults to..."
+                                                               // because clap will automatically
+                                                               // generate that for us, and place
+                                                               // it in the help text
+                                .default_value("input.txt")
+                                .index(1))
+
+                        // Next we'll use the Option::unwrap_or method on this "CONFIG" option
+                        .arg(Arg::with_name("CONFIG")
+                                // Note that we have to manually include some verbiage to the user
+                                // telling them what the default will be.
+                                .help("The config file to use (default is \"config.json\")")
+                                .short("c")
+                                .takes_value(true))
+                        .get_matches();
+
+    // It's safe to call unwrap because the value with either be what the user input at runtime
+    // or "input.txt"
+    let input = matches.value_of("INPUT").unwrap();
+
+    // Using Option::unwrap_or we get the same affect, but without the added help text injection
+    let config_file = matches.value_of("CONFIG").unwrap_or("config.json");
+
+    println!("The input file is: {}", input);
+    println!("The config file is: {}", config_file);
+}