LED Button Service Server GATT code Question:)

Question

Hi!
I'm studying the basic codes of the BLE Blinky Application for peripheral!
(https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.sdk5.v15.0.0%2Fble_sdk_app_blinky.html)

Here I have some questions. Can someone help me find out

1. BLE_LBS_DEF(m_lbs); /**< LED Button Service instance. */
2. NRF_BLE_GATT_DEF(m_gatt); /**< GATT module instance. */
what codes 1 and 2 do? Why do we use these codes?
And what does "instance" exactly mean here?

Thanks:)

awneil · Accepted Answer

They are #defined macros . 
 Use your IDE's code browsing facilities to find the definitions of those macros. 
 What they do is to create the variable given within the parentheses: 
 
 BLE_LBS_DEF( m_lbs ) creates a variable called ' m_lbs ' - this is the data structure used to control the LED Button Service 
 NRF_BLE_GATT_DEF( m_gatt ) creates a variable called ' m_gatt ' - this is the data structure used to control the GATT module 
 
 You will find that Nordic is this approach a lot throughout the SDK. 
 Soojin said: what does "instance" exactly mean here 
 https://en.wiktionary.org/wiki/instantiation

awneil · Answer

For example, we find the definition of NRF_BLE_GATT_DEF() in nrf_ble_gatt.h: 
 /**@brief Macro for defining a nrf_ble_gatt instance.
 *
 * @param _name Name of the instance.
 * @hideinitializer
 */
#define NRF_BLE_GATT_DEF(_name) \
static nrf_ble_gatt_t _name; \
NRF_SDH_BLE_OBSERVER(_name ## _obs, \
 NRF_BLE_GATT_BLE_OBSERVER_PRIO, \
 nrf_ble_gatt_on_ble_evt, &_name)

Note that the created variable is static - Nordic use the m_ prefix to identify file-scope statics

LED Button Service Server GATT code Question:)

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