Create & Delete device resources
Creating Resources
Description
Device with collection resource allows dynamic creation of resources. The created resource can only be of a well defined type (see call to oc_collections_add_rt_factory in Guide) and all created resources are contained within the collection.
Guide
To develop your own device you can examine the example in cloud_server. Lets examine the example to identify the necessary steps that allow a device to dynamically create resources on a collection.
Create a collection resource
oc_resource_t* col = oc_new_collection(NULL, "/switches", 1, 0);
oc_resource_bind_resource_type(col, "oic.wk.col");
For precise description of arguments of given functions please refer to the iotivity-lite documentation.
Determine which resource types can populate the collection
oc_collection_add_supported_rt(col, "oic.r.switch.binary");
Supported resource types are visible through oic.if.baseline interface in a property rts of the collection.
Enable create operation on the collection resource
oc_resource_bind_resource_interface(col, OC_IF_CREATE);
Supporting creating resource is visible through oic.if.baseline interface in a property if of the collection. The property must contains oic.if.create interface.
Define constructor and destructor
oc_collections_add_rt_factory("oic.r.switch.binary", new_switch_instance, free_switch_instance);
typedef struct oc_switch_t
{
struct oc_switch_t *next;
oc_resource_t *resource;
bool state;
} oc_switch_t;
OC_MEMB(switch_s, oc_switch_t, 1);
OC_LIST(switches);
static oc_resource_t*
new_switch_instance(const char* href, oc_string_array_t *types,
oc_resource_properties_t bm, oc_interface_mask_t iface_mask,
size_t device)
{
oc_switch_t *cswitch = (oc_switch_t *)oc_memb_alloc(&switch_s);
if (cswitch) {
cswitch->resource = oc_new_resource(
NULL, href, oc_string_array_get_allocated_size(*types), device);
if (cswitch->resource) {
size_t i;
for (i = 0; i < oc_string_array_get_allocated_size(*types); i++) {
const char *rt = oc_string_array_get_item(*types, i);
oc_resource_bind_resource_type(cswitch->resource, rt);
}
oc_resource_bind_resource_interface(cswitch->resource, iface_mask);
cswitch->resource->properties = bm;
oc_resource_set_default_interface(cswitch->resource, OC_IF_A);
oc_resource_set_request_handler(cswitch->resource, OC_GET, get_cswitch,
cswitch);
oc_resource_set_request_handler(cswitch->resource, OC_DELETE, delete_cswitch,
cswitch);
oc_resource_set_request_handler(cswitch->resource, OC_POST, post_cswitch,
cswitch);
oc_resource_set_properties_cbs(cswitch->resource, get_switch_properties,
cswitch, set_switch_properties, cswitch);
oc_add_resource(cswitch->resource);
oc_set_delayed_callback(cswitch->resource, register_to_cloud, 0);
oc_list_insert(switches, prev, cswitch);
return cswitch->resource;
}
oc_memb_free(&switch_s, cswitch);
}
return NULL;
}
static void
free_switch_instance(oc_resource_t *resource)
{
oc_switch_t *cswitch = (oc_switch_t *)oc_list_head(switches);
while (cswitch) {
if (cswitch->resource == resource) {
oc_delete_resource(resource);
oc_list_remove(switches, cswitch);
oc_memb_free(&switch_s, cswitch);
return;
}
cswitch = oc_list_item_next(cswitch);
}
}
Compile and link
To enable create operation in iotivity-light library compile with CREATE=1 option.
make cloud_server CLOUD=1 SECURE=0 CREATE=1
Create a resource
When you have a cloud backend and cloud_server binary running. You can use cloud client to create a resource.
Using go grpc client
Go grpc client is a simple tool that supports several useful commands we can combine to create a resource.
- Use the get command to identify the collection device
The get command retrieves data of all available devices. To correctly call the create command the device id and href properties are necessary. In the output find the item with type “oic.wk.col”.
// retrieves all resources of all devices
./grpc -get
Output:
...
{
"content": {
"content_type": "application/vnd.ocf+cbor",
"data": "n/8="
},
"resource_id": {
"device_id": "2b9ed3ed-ddf3-4c9c-4d21-9ec1f6ba6b03",
"href": "/switches"
},
"status": 1,
"types": [
"oic.wk.col"
]
}
...
- Create a binary switch resource in the collection
./grpc -create -deviceid 2b9ed3ed-ddf3-4c9c-4d21-9ec1f6ba6b03 -href /switches <<EOF
{
"rt": [
"oic.r.switch.binary"
],
"if": [
"oic.if.a",
"oic.if.baseline"
],
"rep": {
"value": false
},
"p": {
"bm": 3
}
}
EOF
The command creates a binary switch (“oic.r.switch.binary”), which supports actuator interface (“oic.if.a”) and has two possible states (“value”: true/false). The switch is set to be discoverable and observable (“bm”: 3; mask value 3 equals OC_DISCOVERABLE | OC_OBSERVABLE).
- Use the get command again to examine the newly created switch
// retrieves all resources of all devices
./grpc -get
Output:
...
{
"content": {
"content_type": "application/vnd.ocf+cbor",
"data": "v2V2YWx1ZfT/"
},
"resource_id": {
"device_id": "2b9ed3ed-ddf3-4c9c-4d21-9ec1f6ba6b03",
"href": "/4rLN4BlwJmFmbbMJblChB2kyT2zJEP"
},
"status": 1,
"types": [
"oic.r.switch.binary"
]
},
...
Deleting Resources
Description
Device with collection resource allows to delete dynamically created resource. To delete resource you need to set delete handler during creating resource.
Guide
To develop your own device you can examine the example in cloud_server. Lets examine the example to identify the necessary steps that allow a device to delete dynamically created resource at a collection.
Set delete handler at constructor
// delete handler of switch
static void
delete_cswitch(oc_request_t *request, oc_interface_mask_t iface_mask,
void *user_data)
{
OC_DBG("%s", __func__);
(void)request;
(void)iface_mask;
oc_switch_t *cswitch = (oc_switch_t *)user_data;
// cleanup resource data
...
// we cannot delete resource immediately via oc_delete_resource because
// it is used during invocation delete handler. So we plan deleting via oc_delayed_delete_resource call.
oc_delayed_delete_resource(cswitch->resource);
}
static oc_resource_t*
new_switch_instance(const char* href, oc_string_array_t *types,
oc_resource_properties_t bm, oc_interface_mask_t iface_mask,
size_t device)
{
...
oc_resource_set_request_handler(cswitch->resource, OC_GET, get_cswitch,
cswitch);
// set delete handler to the created resource
oc_resource_set_request_handler(cswitch->resource, OC_DELETE, delete_cswitch,
cswitch);
oc_resource_set_request_handler(cswitch->resource, OC_POST, post_cswitch,
cswitch);
...
}
Using go grpc client
Delete a created binary switch resource from the collection.
./grpc -delete -deviceid 2b9ed3ed-ddf3-4c9c-4d21-9ec1f6ba6b03 -href /4rLN4BlwJmFmbbMJblChB2kyT2zJEP