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binder
<binder> tag evaluates to a Binder object.
It mandatorily requires a "var" attribute, which is used as the formal parameter variable in the Binder.bind() method.
Other than that difference, binder tag has the same rule as sequence. They both allow a list of sub-elements that evaluate to Component, they both enforce sequencing. An example would be:
<local> ... <binder id="bean_setter" var="c"> <bean component="$c" autowire="bytype"/> </binder> ... </local>
bind
<bind> tag binds a component and a binder together. For example, we can use the binder we just declared to set properties to an object created by a method:
<method id="acct_before_properties_set" class="BankAccount" name="create" autowire="bytype"/> <bind id="acct_after_properties_set" component="$acct_before_properties_set" binder="$bean_setter"/>
This has exactly the same effect as:
<method id="acct_before_properties_set" class="BankAccount" name="create" autowire="bytype"/> <bean id="acct_after_properties_set" component="$acct_before_properties_set" autowire="bytype"/>
Except that the first example encapsulates part of the dependency injection logic into the binder tag.
callcc
Starting from version 0.7.3, Nuts supports a <callcc> tag that stands for "call-with-current-continuation". "call-with-current-continuation" is a very useful feature that can be found in programming languages such as Scheme and Ruby. I will not cover the details of it here. Please see Scheme callcc and Ruby callcc.
In Nuts, callcc can be used to exit a sequential component combination from the middle. For example:
<callcc exit="return"> ... <call function="$return" args="10"/> <!-- value 10 is returned and components from the point on until the end of the callcc tag are ignored. --> ... </callcc>
<callcc> tag supports an "exit" attribute that is used to specify the name of the exit function. When this function is called anywhere within the scope of <callcc>, the sequential execution is aborted and the function argument is taken as the value of the <callcc> tag.
It should be noted that Nuts' <callcc> is an "escape-only" continuation. Java exception is used to implement the continuation. Therefore, the performance cost of an exception will be paid when <callcc> is used.
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