J2ObjC

Protocol Buffers are Google’s preferred method of representing and communicating structured data. For most Google projects, protocol buffers are used for data storage or client-server communication. As such, a working protocol buffer solution has been a requirement for J2ObjC from day one. Until recently our solution contained internal dependencies that prevented it’s public release, but now I am very pleased to be able to make our internal solution available to all J2ObjC users. Let’s take a quick look at how protocol buffers are used (for a more in-depth look you can read through the Protocol Buffers Developer Guide ). Suppose my app needs a geographic location, so I would create a geo.proto file with the following declaration: message Location {   optional string name = 1;   optional double latitude = 2;   optional double longitude = 3; } Then I can use the protocol buffer compiler, “protoc”, to generate data types in the languages I need: $ protoc --java_out=src...

It's regularly asked why J2ObjC purposely avoids translating UI code; after all, wouldn't it be wonderful if a tool existed where a developer can drop in Android source and out pops an iOS app?

Developers new to J2ObjC may find its "Java compiles to Objective-C, which compiles to .o files" approach a little strange, but it's based on precedent: cfront . When C++ was first released, no compilers translated C++ sources directly into object files. Instead, the cfront script translated C++ into temporary C files, and then invoked cc to compile them. cfront took similar options as cc, so most C++ developers used it as if it was a true C++ compiler. The cfront script wrapped around a transpiler , though; it was a script very similar to combining the j2objc and j2objcc scripts in J2ObjC. One of cfront 's innovations was name mangling , where C++ type information was embedded into C names. J2ObjC also uses name mangling ( described here ) to support features like packages and Java's method overloading semantics that Objective-C doesn't directly support. For example, the JRE has both java.util.Date and java.sql.Date classes; since C names are all ...