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<A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></A>
<UL>
<LI><A NAME="tex2html875"
HREF="node22.html#SECTION00381000000000000000">2.8.1 The control tag</A>
<UL>
<LI><A NAME="tex2html876"
HREF="node22.html#SECTION00381100000000000000">2.8.1.1 Description</A>
<LI><A NAME="tex2html877"
HREF="node22.html#SECTION00381200000000000000">2.8.1.2 Attributes</A>
<LI><A NAME="tex2html878"
HREF="node22.html#SECTION00381300000000000000">2.8.1.3 Examples</A>
</UL>
<BR>
<LI><A NAME="tex2html879"
HREF="node22.html#SECTION00382000000000000000">2.8.2 The outlet tag</A>
<UL>
<LI><A NAME="tex2html880"
HREF="node22.html#SECTION00382100000000000000">2.8.2.1 Description</A>
<LI><A NAME="tex2html881"
HREF="node22.html#SECTION00382200000000000000">2.8.2.2 Attributes</A>
<LI><A NAME="tex2html882"
HREF="node22.html#SECTION00382300000000000000">2.8.2.3 Examples</A>
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<HR>
<H1><A NAME="SECTION00380000000000000000">
2.8 Connector tag reference</A>
</H1>
<P>
<H2><A NAME="SECTION00381000000000000000">
2.8.1 The control tag</A>
</H2>
<P>
<H3><A NAME="SECTION00381100000000000000">
2.8.1.1 Description</A>
</H3>
A <TT><control></TT> tag represents a control connector (a connector
used to connect controls) and is converted into an instance of
<TT>GSMarkupControlConnector</TT>. When the connection is
established, the following code is executed
<PRE>
[source setAction: action];
[source setTarget: target];
</PRE>
where <TT>source</TT> is the source object, <TT>target</TT> is the
target object, and <TT>action</TT> is obtained by converting the
action attribute into a selector.
<P>
Because objects which allow you to set an action normally have an
action attribute, this connector is normally never used, since you
would rather set the action of the source by using the action
attribute of the source object, and then set the target of the source
to the target object by using a standard outlet connector with key
"target", or setting the object attribute target of the source to the
target object. Please have a look at the examples which should make
this clear.
<P>
<H3><A NAME="SECTION00381200000000000000">
2.8.1.2 Attributes</A>
</H3>
<UL>
<LI><B>action</B>: The action of the connector. This attribute is a
string (non localizable), which is converted into a selector when
the connection is established. If missing (or if the specified
selector can't be found), a <TT>NULL</TT> action is used.
</LI>
<LI><B>label</B>: If there is no <TT>action</TT> but a <TT>label</TT>
attribute is present, it is used instead of <TT>action</TT>.
</LI>
<LI><B>source</B>: A reference to another object - a string
beginning with a hash (<TT>#</TT>). This object is the source of
the control connector. If the string contains a dot, the object is
looked up in the name table, and then key-value coding is applied
(see the description of advanced outlets). It is required.
</LI>
<LI><B>target</B>: A reference to another object - a string
beginning with a hash (<TT>#</TT>). This object is the target of
the control connector. If the string contains a dot, the object is
looked up in the name table, and then key-value coding is applied
(see the description of advanced outlets). If omitted, <TT>nil</TT>
will be used as target when establishing the connection.
</LI>
</UL>
<P>
<H3><A NAME="SECTION00381300000000000000">
2.8.1.3 Examples</A>
</H3>
Control connectors are used very rarely. Here is how a control
connector would look:
<PRE>
<connectors>
<control source="#myButton" target="#myController" action="buttonPressed:" />
</connectors>
</PRE>
this is rarely used, because usually you can more simply do
<PRE>
<objects>
...
<button action="buttonPressed:" target="#myController" ... />
...
</objects>
</PRE>
this is equivalent, but it is preferred because it is much more
natural: you set the action and the target of the button in the same
place where you create the button, rather than in the separate
connectors section. The system automatically writes all action
connectors in this way when it writes gsmarkup files - if it can: if the
source is not created in the gsmarkup file, this can't be done, and you
would need to use a control connector explicitly.
<P>
<H2><A NAME="SECTION00382000000000000000">
2.8.2 The outlet tag</A>
</H2>
<P>
<H3><A NAME="SECTION00382100000000000000">
2.8.2.1 Description</A>
</H3>
An <TT><outlet></TT> tag represents an outlet connector (a generic
connector), and is converted into an instance of
<TT>GSMarkupOutletConnector</TT>. When the connection is established,
the following code is executed
<PRE>
[source takeValue: target forKey: key];
</PRE>
where <TT>source</TT> is the source object, <TT>target</TT> is the
target object, and <TT>label</TT> is the key. Often an outlet can be
embedded directly into the objects section, which results in simpler,
better code.
<P>
<H3><A NAME="SECTION00382200000000000000">
2.8.2.2 Attributes</A>
</H3>
<UL>
<LI><B>key</B>: The key of the connector. This attribute is a string
(non localized), and is required (unless a label is provided). It
is the key whose value is set to target, using key-value coding on
source.
</LI>
<LI><B>label</B>: If there is no <TT>key</TT> but a <TT>label</TT>
attribute is present, it is used instead of <TT>key</TT>.
</LI>
<LI><B>source</B>: A reference to another object - a string
beginning with a hash (<TT>#</TT>). This object is the source of
the outlet connector. If the string contains a dot, the object is
looked up in the name table, and then key-value coding is applied
(see the description of advanced outlets). It is required.
</LI>
<LI><B>target</B>: A reference to another object - a string
beginning with a hash (<TT>#</TT>). This object is the target of
the outlet connector. If the string contains a dot, the object is
looked up in the name table, and then key-value coding is applied
(see the description of advanced outlets). If omitted, <TT>nil</TT>
will be used as target when establishing the connection.
</LI>
</UL>
<P>
<H3><A NAME="SECTION00382300000000000000">
2.8.2.3 Examples</A>
</H3>
Outlet connectors are not used often, but they are needed sometimes.
Here is how an outlet connector would look:
<PRE>
<connectors>
<outlet source="#myController" target="#myButton" key="button" />
</connectors>
</PRE>
this (in which the source is an object already existing in the
application) is the only form of outlet connector which is normally
used, because if the object is created in the gsmarkup file itself, the outlet
can be embedded in the object creation by using the syntax
<PRE>
<objects>
...
<textView delegate="#myController" ... />
...
</objects>
</PRE>
which is perfectly equivalent to:
<PRE>
<objects>
...
<textView id="myTextView" ... />
...
</objects>
<connectors>
<outlet source="#myTextView" target="#myController" key="delegate" />
</connectors>
</PRE>
this second explicit form is much more long, artificial and
cumbersome. The system automatically writes all outlet connectors
inside the objects section when it writes gsmarkup files - if it can. In
some cases (when the source is created outside the gsmarkup file) this
can't be done; these are the cases in which the connector is created
manually inside the connectors section.
<P>
<HR><B> Next: <A NAME="tex2html874"
HREF="node23.html">2.9 Example</A> </B>
<B>Up: <A NAME="tex2html870"
HREF="node14.html">2. The GNUstep Markup</A> </B>
<B> Previous: <A NAME="tex2html864"
HREF="node21.html">2.7 Object tag reference</A> </B>
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