Struct ArgGroup

pub struct ArgGroup<'a> { /* private fields */ }

ArgGroups are a family of related arguments and way for you to express, “Any of these arguments”. By placing arguments in a logical group, you can create easier requirement and exclusion rules instead of having to list each argument individually, or when you want a rule to apply “any but not all” arguments.

For instance, you can make an entire ArgGroup required. If ArgGroup::multiple(true) is set, this means that at least one argument from that group must be present. If [ArgGroup::multiple(false)] is set (the default), one and only one must be present.

You can also do things such as name an entire ArgGroup as a conflict or requirement for another argument, meaning any of the arguments that belong to that group will cause a failure if present, or must present respectively.

Perhaps the most common use of ArgGroups is to require one and only one argument to be present out of a given set. Imagine that you had multiple arguments, and you want one of them to be required, but making all of them required isn’t feasible because perhaps they conflict with each other. For example, lets say that you were building an application where one could set a given version number by supplying a string with an option argument, i.e. --set-ver v1.2.3, you also wanted to support automatically using a previous version number and simply incrementing one of the three numbers. So you create three flags --major, --minor, and --patch. All of these arguments shouldn’t be used at one time but you want to specify that at least one of them is used. For this, you can create a group.

Finally, you may use ArgGroups to pull a value from a group of arguments when you don’t care exactly which argument was actually used at runtime.

Examples

The following example demonstrates using an ArgGroup to ensure that one, and only one, of the arguments from the specified group is present at runtime.

let result = App::new("app")
    .args_from_usage(
        "--set-ver [ver] 'set the version manually'
         --major         'auto increase major'
         --minor         'auto increase minor'
         --patch         'auto increase patch'")
    .group(ArgGroup::with_name("vers")
         .args(&["set-ver", "major", "minor", "patch"])
         .required(true))
    .get_matches_from_safe(vec!["app", "--major", "--patch"]);
// Because we used two args in the group it's an error
assert!(result.is_err());
let err = result.unwrap_err();
assert_eq!(err.kind, ErrorKind::ArgumentConflict);

This next example shows a passing parse of the same scenario

let result = App::new("app")
    .args_from_usage(
        "--set-ver [ver] 'set the version manually'
         --major         'auto increase major'
         --minor         'auto increase minor'
         --patch         'auto increase patch'")
    .group(ArgGroup::with_name("vers")
         .args(&["set-ver", "major", "minor","patch"])
         .required(true))
    .get_matches_from_safe(vec!["app", "--major"]);
assert!(result.is_ok());
let matches = result.unwrap();
// We may not know which of the args was used, so we can test for the group...
assert!(matches.is_present("vers"));
// we could also alternatively check each arg individually (not shown here)

Implementations

impl<'a> ArgGroup<'a>

pub fn with_name(n: &'a str) -> ArgGroup<'a>

Creates a new instance of ArgGroup using a unique string name. The name will be used to get values from the group or refer to the group inside of conflict and requirement rules.

Examples

ArgGroup::with_name("config")

pub fn arg(self, n: &'a str) -> ArgGroup<'a>

Adds an argument to this group by name

Examples

let m = App::new("myprog")
    .arg(Arg::with_name("flag")
        .short("f"))
    .arg(Arg::with_name("color")
        .short("c"))
    .group(ArgGroup::with_name("req_flags")
        .arg("flag")
        .arg("color"))
    .get_matches_from(vec!["myprog", "-f"]);
// maybe we don't know which of the two flags was used...
assert!(m.is_present("req_flags"));
// but we can also check individually if needed
assert!(m.is_present("flag"));

pub fn args(self, ns: &[&'a str]) -> ArgGroup<'a>

Adds multiple arguments to this group by name

Examples

let m = App::new("myprog")
    .arg(Arg::with_name("flag")
        .short("f"))
    .arg(Arg::with_name("color")
        .short("c"))
    .group(ArgGroup::with_name("req_flags")
        .args(&["flag", "color"]))
    .get_matches_from(vec!["myprog", "-f"]);
// maybe we don't know which of the two flags was used...
assert!(m.is_present("req_flags"));
// but we can also check individually if needed
assert!(m.is_present("flag"));

pub fn multiple(self, m: bool) -> ArgGroup<'a>

Allows more than one of the ‘Arg’s in this group to be used. (Default: false)

Examples

Notice in this example we use both the -f and -c flags which are both part of the group

let m = App::new("myprog")
    .arg(Arg::with_name("flag")
        .short("f"))
    .arg(Arg::with_name("color")
        .short("c"))
    .group(ArgGroup::with_name("req_flags")
        .args(&["flag", "color"])
        .multiple(true))
    .get_matches_from(vec!["myprog", "-f", "-c"]);
// maybe we don't know which of the two flags was used...
assert!(m.is_present("req_flags"));

In this next example, we show the default behavior (i.e. `multiple(false)) which will throw an error if more than one of the args in the group was used.

let result = App::new("myprog")
    .arg(Arg::with_name("flag")
        .short("f"))
    .arg(Arg::with_name("color")
        .short("c"))
    .group(ArgGroup::with_name("req_flags")
        .args(&["flag", "color"]))
    .get_matches_from_safe(vec!["myprog", "-f", "-c"]);
// Because we used both args in the group it's an error
assert!(result.is_err());
let err = result.unwrap_err();
assert_eq!(err.kind, ErrorKind::ArgumentConflict);

pub fn required(self, r: bool) -> ArgGroup<'a>

Sets the group as required or not. A required group will be displayed in the usage string of the application in the format <arg|arg2|arg3>. A required ArgGroup simply states that one argument from this group must be present at runtime (unless conflicting with another argument).

NOTE: This setting only applies to the current App / SubCommand, and not globally.

NOTE: By default, ArgGroup::multiple is set to false which when combined with ArgGroup::required(true) states, “One and only one arg must be used from this group. Use of more than one arg is an error.” Vice setting ArgGroup::multiple(true) which states, ’At least one arg from this group must be used. Using multiple is OK.“

Examples

let result = App::new("myprog")
    .arg(Arg::with_name("flag")
        .short("f"))
    .arg(Arg::with_name("color")
        .short("c"))
    .group(ArgGroup::with_name("req_flags")
        .args(&["flag", "color"])
        .required(true))
    .get_matches_from_safe(vec!["myprog"]);
// Because we didn't use any of the args in the group, it's an error
assert!(result.is_err());
let err = result.unwrap_err();
assert_eq!(err.kind, ErrorKind::MissingRequiredArgument);

pub fn requires(self, n: &'a str) -> ArgGroup<'a>

Sets the requirement rules of this group. This is not to be confused with a required group. Requirement rules function just like argument requirement rules, you can name other arguments or groups that must be present when any one of the arguments from this group is used.

NOTE: The name provided may be an argument, or group name

Examples

let result = App::new("myprog")
    .arg(Arg::with_name("flag")
        .short("f"))
    .arg(Arg::with_name("color")
        .short("c"))
    .arg(Arg::with_name("debug")
        .short("d"))
    .group(ArgGroup::with_name("req_flags")
        .args(&["flag", "color"])
        .requires("debug"))
    .get_matches_from_safe(vec!["myprog", "-c"]);
// because we used an arg from the group, and the group requires "-d" to be used, it's an
// error
assert!(result.is_err());
let err = result.unwrap_err();
assert_eq!(err.kind, ErrorKind::MissingRequiredArgument);

pub fn requires_all(self, ns: &[&'a str]) -> ArgGroup<'a>

Sets the requirement rules of this group. This is not to be confused with a required group. Requirement rules function just like argument requirement rules, you can name other arguments or groups that must be present when one of the arguments from this group is used.

NOTE: The names provided may be an argument, or group name

Examples

let result = App::new("myprog")
    .arg(Arg::with_name("flag")
        .short("f"))
    .arg(Arg::with_name("color")
        .short("c"))
    .arg(Arg::with_name("debug")
        .short("d"))
    .arg(Arg::with_name("verb")
        .short("v"))
    .group(ArgGroup::with_name("req_flags")
        .args(&["flag", "color"])
        .requires_all(&["debug", "verb"]))
    .get_matches_from_safe(vec!["myprog", "-c", "-d"]);
// because we used an arg from the group, and the group requires "-d" and "-v" to be used,
// yet we only used "-d" it's an error
assert!(result.is_err());
let err = result.unwrap_err();
assert_eq!(err.kind, ErrorKind::MissingRequiredArgument);

pub fn conflicts_with(self, n: &'a str) -> ArgGroup<'a>

Sets the exclusion rules of this group. Exclusion (aka conflict) rules function just like argument exclusion rules, you can name other arguments or groups that must not be present when one of the arguments from this group are used.

NOTE: The name provided may be an argument, or group name

Examples

let result = App::new("myprog")
    .arg(Arg::with_name("flag")
        .short("f"))
    .arg(Arg::with_name("color")
        .short("c"))
    .arg(Arg::with_name("debug")
        .short("d"))
    .group(ArgGroup::with_name("req_flags")
        .args(&["flag", "color"])
        .conflicts_with("debug"))
    .get_matches_from_safe(vec!["myprog", "-c", "-d"]);
// because we used an arg from the group, and the group conflicts with "-d", it's an error
assert!(result.is_err());
let err = result.unwrap_err();
assert_eq!(err.kind, ErrorKind::ArgumentConflict);

pub fn conflicts_with_all(self, ns: &[&'a str]) -> ArgGroup<'a>

Sets the exclusion rules of this group. Exclusion rules function just like argument exclusion rules, you can name other arguments or groups that must not be present when one of the arguments from this group are used.

NOTE: The names provided may be an argument, or group name

Examples

let result = App::new("myprog")
    .arg(Arg::with_name("flag")
        .short("f"))
    .arg(Arg::with_name("color")
        .short("c"))
    .arg(Arg::with_name("debug")
        .short("d"))
    .arg(Arg::with_name("verb")
        .short("v"))
    .group(ArgGroup::with_name("req_flags")
        .args(&["flag", "color"])
        .conflicts_with_all(&["debug", "verb"]))
    .get_matches_from_safe(vec!["myprog", "-c", "-v"]);
// because we used an arg from the group, and the group conflicts with either "-v" or "-d"
// it's an error
assert!(result.is_err());
let err = result.unwrap_err();
assert_eq!(err.kind, ErrorKind::ArgumentConflict);

Trait Implementations

impl<'a> Clone for ArgGroup<'a>

fn clone(&self) -> ArgGroup<'a>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'a> Debug for ArgGroup<'a>

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<'a> Default for ArgGroup<'a>

fn default() -> ArgGroup<'a>

Returns the “default value” for a type.

impl<'a, 'z> From<&'z ArgGroup<'a>> for ArgGroup<'a>

fn from(g: &'z ArgGroup<'a>) -> ArgGroup<'a>

Converts to this type from the input type.