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Dynamically Setting Up a Machine

Retomus allows you to reconfigure a machine at runtime using the .setup() method.
This is useful for injecting dynamic values, overriding handlers, or preparing the machine for specific flows.

🔧 Basic Example​

useEffect(() => {
  counterMachine.setup({
    ctx: {
      state: { count: 10 },
      sv: { countSharedValue: 5 },
    },
    actionHandlers: {
      increment: ({ ctx, done }) => {
        ctx.state.count += 2;
        done();
      },
    },
  });
}, []);

This redefines both the context values and the increment logic at runtime.

🧰 Supported Fields in setup()​

FieldDescription
ctxNew context data (state, sv, ref)
actionHandlersRuntime handler overrides
options.ctx.overwriteWhether to replace or merge context

📎 Overwriting vs Merging Context​

By default, context is merged:

setup({ ctx: { state: { count: 1 } } });

To completely replace context:

setup({
  ctx: {
    state: { count: 1 },
  },
  options: {
    ctx: {
      overwrite: true,
    },
  },
});

🔁 When to use setup()​

  • Injecting test-specific behavior
  • Bootstrapping from localStorage
  • Changing behavior based on user type
  • Implementing machine reuse with different logic

⚠️ Caution​

  • Only call .setup() once after machine creation
  • Changing logic mid-flight may cause unexpected side effects if not isolated

🔗 Related​