[groovy] groovy dynamic language features (automatic type inference of function arguments in groovy | precautions for function dynamic parameters)

Preface

Groovy It's dynamic language , Java It's a static language ;

This blog discussion Groovy in , Automatic type inference of function arguments ;

One 、Groovy Automatic type inference of function arguments in

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Define two different classes Student and Worker , Define in the class hello Method ;

class Student { 
        def hello(){ 
            println "Hello Student"    }}class Worker { 
        def hello(){ 
            println "Hello Worker"    }}

Declare a method , Receiving parameters object , The parameter type is not specified temporarily , Call the... Of the parameter object in the function hello Method ;

void fun(object) { 
        object.hello()}

Report to the fun Function passed in Student and Worker object , Then... In the corresponding class will be called respectively hello Method ;

fun(new Student())fun(new Worker())

Two 、 Precautions for function dynamic parameters

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Special attention should be paid here , Don't pass the wrong object , If there is no definition in the class hello Method , It can be compiled through , But the runtime will report an error ;

Such as : Defined a no hello Class of method ,

class Farmer { 
    }

The instance object of this class is passed in fun Method as parameter ,

fun(new Farmer())

The following error will be reported :

Caught: groovy.lang.MissingMethodException: No signature of method: Farmer.hello() is applicable for argument types: () values: []Possible solutions: sleep(long), sleep(long, groovy.lang.Closure), getAt(java.lang.String), each(groovy.lang.Closure), split(groovy.lang.Closure), wait()groovy.lang.MissingMethodException: No signature of method: Farmer.hello() is applicable for argument types: () values: []Possible solutions: sleep(long), sleep(long, groovy.lang.Closure), getAt(java.lang.String), each(groovy.lang.Closure), split(groovy.lang.Closure), wait()	at Worker$hello.call(Unknown Source)	at Groovy.fun(Groovy.groovy:17)	at Groovy$fun.callCurrent(Unknown Source)	at Groovy.run(Groovy.groovy:22)

To avoid the above problems , You can use @TypeChecked annotation , But the corresponding , It's lost Groovy The dynamics of language ;

@TypeCheckedvoid fun(Student object) { 
        object.hello()}

3、 ... and 、 Complete code example

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Complete code example :

class Student { 
        def hello(){ 
            println "Hello Student"    }}class Worker { 
        def hello(){ 
            println "Hello Worker"    }}class Farmer { 
    }void fun(object) { 
        object.hello()}fun(new Student())fun(new Worker())//  The following usage will report  Caught: groovy.lang.MissingMethodException  abnormal //fun(new Farmer())

Execution results :

Hello StudentHello Worker