Appropriate mutation

example.js

// HELPER at top of file, or in util
const cloneSetAllSelected = (serviceHosts, selected: boolean = false) => {
  return serviceHosts.map(service => ({
    ...service,
    selected,
    hosts: service.hosts.map(host => ({
      ..host,
      selected
    }))
  }));
}

selectExisting(
  context: StateContext<ServiceDetailDialogModel>,
  { payload: {
    existingServiceHosts
  } }: ServiceDetailDialogActions.SelectExisting) {
  // Reset any previous state:
  const { serviceHosts } = context.getState();
  context.patchState({
    serviceHosts: cloneSetAllSelected(serviceHosts, false)
  });                           
}

reset(context: StateContext<ServiceDetailDialogModel>) {
  const { serviceHosts } = context.getState();
  context.patchState({
    serviceFilter: '',
    hostFilter: ''
    serviceHosts: cloneSetAllSelected(serviceHosts, false)
  });
}