iostream.stream.writeobject

Serializes the object to the stream

from "iostream" import blob

let squadIds = blob(0)
squadIds.writeobject([101, 102, 103])

squadIds.seek(0)
let back = squadIds.readobject()
println("back[0], back[1], back[2] =", $"{back[0]},{back[1]},{back[2]}")

back[0], back[1], back[2] = 101,102,103

Parameters

Errors

Throws Unsupported object type for serialization for a value writeobject cannot encode: a function, generator, thread, weakref, userdata or userpointer, whether obj is that value itself or it turns up nested inside an array or table.

An instance of a class needs classes to name that class, and the class needs a __getstate method that returns the state to save:

• Unsupported class for serialization - the instance's class is not a key in classes (including when classes was not passed)
• Instance must have __getstate method for serialization - the class has no __getstate
• Instance method __getstate must be a closure - the class has a __getstate slot, but it is not callable

Notes

The same method works on a file. Writing past the current len grows a blob to fit, the same as writen.

iostream.stream.readobject reverses this: pairing the two on the same stream round-trips a value, provided classes lists every class either side needs.

Example

from "iostream" import blob

let b = blob(0)
b.writeobject([1, 2])
println("b.len() =", b.len()) // a start marker, the encoded array, an end marker

class Point { function __getstate() { return 1 } function __setstate(s) {} }
try { b.writeobject(Point()) } catch (e) { println("b.writeobject(Point()) throws:", e) } // no classes table passed

try { b.writeobject(print) } catch (e) { println("b.writeobject(print) throws:", e) } // a function cannot be serialized

b.len() = 6
b.writeobject(Point()) throws: Unsupported class for serialization
b.writeobject(print) throws: Unsupported object type for serialization

See also