# macrodef

Tag: macrodef
Defines a new dependency resolver type based upon another. This definition is very similar to the macrodef feature of ant for defining macro tasks. since 1.3 This task eases the process of creating a new dependency resolver, because it avoids writing java code.
It is generally used in combination with the include feature to help reuse a macro in multiple settings files.
A macro is defined by declaring an existing resolver within it. Then you can use attributes to pass parameters to the newly defined resolver type. Attributes are defined with a name, and optionally a default value, and are used using the following syntax:

    @{attributename}

## Resolvers names

Since you can use the same macro several times it can define several resolvers (in a chain for instance), the resolver names need to be chosen carefully to avoid name conflicts (each resolver must have a unique name).
Here is how Ivy deals with the names of the resolvers defined in a macro:

- if there is no name attribute on a resolver in the macrodef, then Ivy will use the name given when using the macro. This is what usually should be done for the main resolver defined in the macro
- if there is a name attribute on a resolver in the macrodef, but this name doesn't contain a @{name} inside, then Ivy will use the provided name prefixed with the name of the macro separated by a dash
- if there is a name attribute on a resolver in the macrodef, and this name contains @{name} somewhere, then Ivy will use this name, and replace @{name} with the name provided when using the macro.

Example:

    <ivysettings>
      <macrodef name="mymacro">
        <chain>
          <ibiblio name="ex1" />
          <ibiblio name="ex2.@{name}" m2compatible="true" />
        </chain>
      </macrodef>

      <resolvers>
        <mymacro name="default" />
        <mymacro name="other" />
       </resolvers>
    </ivysettings>

This is equivalent to:

    <ivysettings>
      <resolvers>
        <chain name="default">
          <ibiblio name="default-ex1" />
          <ibiblio name="ex2.default" m2compatible="true" />
        </chain>
        <chain name="other">
          <ibiblio name="other-ex1" />
          <ibiblio name="ex2.other" m2compatible="true" />
        </chain>
       </resolvers>
    </ivysettings>

# Attributes

Attribute | Description | Required
--- | --- | ---
name | name of the resover type created | Yes

# Child elements

Element | Description | Cardinality
--- | --- | ---
attribute | defines an attribute for the macro resolver | 0..n
any resolver | defines the base resolver upon which this macro is defined | 1

# Examples

Defining a simple macro:

      <macrodef name="mymacro">
        <attribute name="mymainrep"/>
          <filesystem name="fs1">
            <ivy pattern="@{mymainrep}/[organisation]/[module]/[type]s/[artifact]-[revision].[ext]"/>
            <artifact pattern="@{mymainrep}/[organisation]/[module]/[type]s/[artifact]-[revision].[ext]"/>
          </filesystem>
      </macrodef>

Using it:

      <resolvers>
        <mymacro name="default" mymainrep="path/to/myrep"/>
      </resolvers>

A complete example:

    <ivysettings>
      <macrodef name="mymacro">
        <attribute name="mymainrep"/>
        <attribute name="mysecondrep"/>
        <attribute name="myseconddirlayout" default="[organisation]/[module]/[type]s"/>
        <chain>
          <filesystem name="fs1">
            <ivy pattern="@{mymainrep}/[organisation]/[module]/[type]s/[artifact]-[revision].[ext]"/>
            <artifact pattern="@{mymainrep}/[organisation]/[module]/[type]s/[artifact]-[revision].[ext]"/>
          </filesystem>
          <filesystem name="fs2" latest="latest-time">
            <ivy pattern="@{mysecondrep}/@{myseconddirlayout}/ivy-[revision].xml"/>
            <artifact pattern="@{mysecondrep}/@{myseconddirlayout}/[artifact]-[revision].[ext]"/>
          </filesystem>
        </chain>
      </macrodef>

      <resolvers>
        <mymacro name="default" mymainrep="path/to/myrep" mysecondrep="path/to/secondrep"/>
        <mymacro name="other"
           mymainrep="path/to/myrep"
           mysecondrep="path/to/secondrep"
           myseconddirlayout="[module]/[type]s"/>
       </resolvers>
    </ivysettings>