digitalmars.D.learn - deserialization: creating a class instance without calling constructor
- Timothee Cour via Digitalmars-d-learn (14/14) May 21 2015 Can I create an instance of A without calling a constructor? (see below)
- John Colvin (4/23) May 21 2015 For a start I'm pretty sure you want to be calling
- Baz (15/34) May 21 2015 based on this:
- Jacob Carlborg (6/21) May 21 2015 Here's how I do it in my serialization library Orange [1]
- timotheecour (2/30) May 25 2015 Thanks!
Can I create an instance of A without calling a constructor? (see below) Use case: for generic deserialiaztion, when the deserialization library encounters a class without default constructor for example (it knows what the fields should be set to, but doesn't know how to construct the object). class A{ int x=2; this(int x){ this.x=x; } } This came up here: https://github.com/msgpack/msgpack-d/issues/54#issuecomment-104136148 I provide some hacky solution for that in that thread but I suspect it's not safe and something is missing.
May 21 2015
On Thursday, 21 May 2015 at 09:06:59 UTC, Timothee Cour wrote:Can I create an instance of A without calling a constructor? (see below) Use case: for generic deserialiaztion, when the deserialization library encounters a class without default constructor for example (it knows what the fields should be set to, but doesn't know how to construct the object). class A{ int x=2; this(int x){ this.x=x; } } This came up here: https://github.com/msgpack/msgpack-d/issues/54#issuecomment-104136148 I provide some hacky solution for that in that thread but I suspect it's not safe and something is missing.For a start I'm pretty sure you want to be calling core.memory.GC.malloc not core.stdc.stdlib.malloc, otherwise you leak the memory.
May 21 2015
On Thursday, 21 May 2015 at 09:06:59 UTC, Timothee Cour wrote:Can I create an instance of A without calling a constructor? (see below) Use case: for generic deserialiaztion, when the deserialization library encounters a class without default constructor for example (it knows what the fields should be set to, but doesn't know how to construct the object). class A{ int x=2; this(int x){ this.x=x; } } This came up here: https://github.com/msgpack/msgpack-d/issues/54#issuecomment-104136148 I provide some hacky solution for that in that thread but I suspect it's not safe and something is missing.based on this: https://github.com/D-Programming-Language/druntime/blob/6698ee21d4eb00ec2e8c621993359d235618df75/src/rt/lifetime.d#L71 you can create an instance without calling the constructor like this: --- CT construct(CT, A...)(A a) if (is(CT == class)) { auto memory = malloc(typeid(CT).init.length); memory[0 .. typeid(CT).init.length] = typeid(CT).init[]; return cast(CT) memory; } --- actually it only copies the fields with their initial values.
May 21 2015
On 2015-05-21 11:06, Timothee Cour via Digitalmars-d-learn wrote:Can I create an instance of A without calling a constructor? (see below) Use case: for generic deserialiaztion, when the deserialization library encounters a class without default constructor for example (it knows what the fields should be set to, but doesn't know how to construct the object). class A{ int x=2; this(int x){ this.x=x; } } This came up here: https://github.com/msgpack/msgpack-d/issues/54#issuecomment-104136148 I provide some hacky solution for that in that thread but I suspect it's not safe and something is missing.Here's how I do it in my serialization library Orange [1] [1] https://github.com/jacob-carlborg/orange/blob/master/orange/util/Reflection.d#L166 -- /Jacob Carlborg
May 21 2015
On Thursday, 21 May 2015 at 19:06:35 UTC, Jacob Carlborg wrote:On 2015-05-21 11:06, Timothee Cour via Digitalmars-d-learn wrote:Thanks!Can I create an instance of A without calling a constructor? (see below) Use case: for generic deserialiaztion, when the deserialization library encounters a class without default constructor for example (it knows what the fields should be set to, but doesn't know how to construct the object). class A{ int x=2; this(int x){ this.x=x; } } This came up here: https://github.com/msgpack/msgpack-d/issues/54#issuecomment-104136148 I provide some hacky solution for that in that thread but I suspect it's not safe and something is missing.Here's how I do it in my serialization library Orange [1] [1] https://github.com/jacob-carlborg/orange/blob/master/orange/util/Reflection.d#L166
May 25 2015