esp-nimble-cpp/docs/Improvements_and_updates.md

# Improvements and updates

# Server  

NimBLECharacteristic::setValue(const T &s)  
NimBLEDescriptor::setValue(const T &s)  

Now use a template to accomodate standard and custom types/values.  

**Example**
```
struct my_struct{
    uint8_t  one;
    uint16_t two;
    uint32_t four;
    uint64_t eight;
    float    flt;
}myStruct;
        
    myStruct.one = 1;
    myStruct.two = 2;
    myStruct.four = 4;
    myStruct.eight = 8;
    myStruct.flt = 1234.56;

    pCharacteristic->setValue(myStruct);
 ```
This will send the struct to the recieving client when read or a notification sent.  

NimBLECharacteristic::getValue now takes an optional timestamp parameter which will update it's value with  
the time the last value was recieved. In addition an overloaded template has been added to retrieve the value  
as a type specified by the user.  

**Example**
```
    time_t timestamp;
    myStruct = pCharacteristic->getValue<myStruct>(&timestamp); // timestamp optional
```
<br/>

**Advertising will automatically start when a client disconnects.**  

A new method `NimBLEServer::advertiseOnDisconnect(bool)` has been implemented to control this, true(default) = enabled.  
<br/>

`NimBLEServer::removeService` takes an additional parameter `bool deleteSvc` that if true will delete the service  
and all characteristics / descriptors belonging to it and invalidating any pointers to them.  
If false the service is only removed from visibility by clients. The pointers to the service and  
it's characteristics / descriptors will remain valid and the service can be re-added in the future  
using `NimBLEServer::addService`.  
<br/>

New characteristic read/write callbacks added to NimBLECharacteristicCallbacks that receive a pointer to the connection  
description of the client reading/writing.  
This is useful when connected to multiple clients to discern which client is performing the operation.
<br/>

# Client  

NimBLERemoteCharacteristic::readValue(time_t\*, bool)  
NimBLERemoteDescriptor::readValue(bool)  

Have been added as templates to allow reading the values as any specified type.   

**Example**
```
struct my_struct{
    uint8_t  one;
    uint16_t two;
    uint32_t four;
    uint64_t eight;
    float    flt;
}myStruct;

    time_t timestamp;
    myStruct = pRemoteCharacteristic->readValue<myStruct>(&timestamp); // timestamp optional
```  
<br/>

NimBLERemoteCharacteristic::registerForNotify  
Has been **deprecated** as now the internally stored characteristic value is updated when notification/indication is recieved.  

NimBLERemoteCharacteristic::subscribe and NimBLERemoteCharacteristic::unsubscribe have been implemented to replace it.  
A callback is no longer requred to get the most recent value unless timing is important. Instead, the application can call NimBLERemoteCharacteristic::getValue to  
get the last updated value any time.  

In addition NimBLERemoteCharacteristic::readValue and NimBLERemoteCharacteristic::getValue take an optional timestamp parameter which will update it's value with  
the time the last value was recieved.  

NimBLEClient::getService will now retrieve only the service specified and not the full database, this preserves resources  
otherwise wasted retrieving and allocating attributes the user application is not interested in.  
<br/>

# General  
To reduce resource use all instances of std::map have been replaced with std::vector.  

Use of FreeRTOS::Semaphore has been removed as it was consuming too much ram, the related files have been left in place to accomodate application use.  

Operators `==`, `!=` and `std::string` have been added to NimBLEAddress and NimBLEUUID for easier comparison and logging.  

New constructor for NimBLEUUID(uint32_t, uint16_t, uint16_t, uint64_t) added to lower memory use vs string construction. See: [#21](https://github.com/h2zero/NimBLE-Arduino/pull/21).   

Security/pairing operations are now handled in the respective NimBLEClientCallbacks and NimBLEServerCallbacks classes, NimBLESecurity(deprecated) remains for backward compatibility.  

Configuration options have been added to add or remove debugging information, when disabled (default) significatly reduces binary size.  
In ESP-IDF the options are in menuconfig: `Main menu -> ESP-NimBLE-cpp configuration`.  
For Arduino the options must be commented / uncommented in nimconfig.h.   

Many more internal improvements have been made as well, this is a brief overview. Refer to the class docs for futher information on class specifics.  
<br/>