Data type and annotation types in the J2Objc Annotations framework

Data type and annotation type in J2Objc Annotations framework J2OBJC is a tool for converting Java code into Objective-C code. When converting Java code into Objective-C code, sometimes it is necessary to add annotations to specific code elements.To meet this demand, J2OBJC provides an annotation framework that contains some types of annotations for specifying specific attributes and behaviors. Note type is a special type used in Java, which can add meta data to program elements (such as class, methods, fields, etc.).In J2Objc, there are several main types of annotations that can be used to specify behaviors during conversion. 1. @Mapping: This annotation can be used to mark the mapping relationship between a class between an Objective-C class and its corresponding Java class.This annotation can be used for classifications and attribute declarations. Below is an example of using @mapping annotation: @Mapping ("Person") // Map the Java Person as Objective-C Person public class Person { @Mapping ("name") // Map the Java attribute name as Objective-C attribute name private String name; // omit other code } 2. @Mappingqualifier: This annotation is used to mark a value type, which must have certain specific attributes at the same time.This annotation is mainly used for the attributes of the Objective-C collection types such as NSARAY, NSDictionary, and NSString. Below is an example of using @mappingqualifier annotation: @Mappingqualifier // Specify the value of the attribute must be NSSTRING @interface MyString {} @Mapping("Person") public class Person { @Mappingqualifier (mystring.class) // The value of limited name properties is NSSTRING private String name; // omit other code } 3. @Weak: This annotation can be used to mark a attribute, indicating that the corresponding Objective-C attribute is weak reference.When converting to Objective-C code, using this annotation can automatically generate appropriate memory management code for the attributes of the reference type. The following is an example of using @weak annotation: @Mapping("Person") public class Person { @Weak // State the adDRESS attribute to weak reference private Address address; // omit other code } The above code indicates that the address property in the Person class is a weak reference.When converting to Objective-C code, J2OBJC will automatically generate the corresponding weak reference to this attribute. The J2OBJC annotation framework provides these major types of annotations that can help developers perform more detailed control and customization when converting Java code into Objective-C code. Summary: The annotation type in the J2Objc Annotations framework can be used to specify the mapping relationship, limited value type, and weak references during the conversion.Developers can use these annotations to provide more metadata as a code to better control the conversion behavior of the code. I hope this article will help you understand the data types and annotation types in the J2Objc Annotations framework.