feat: provide setting to use only non-cellular, inexpensive and non-constrained network for sending logged events to Amplitude servers

Sources/Amplitude/AMPIdentify.m

@@ -130,8 +130,19 @@ - (void)addToUserProperties:(NSString *)operation property:(NSString *)property
 
     // Check if property was already used in a previous operation.
     if ([_userProperties containsObject:property]) {
-        AMPLITUDE_LOG(@"Already used property '%@' in previous operation, ignoring for operation '%@'", property, operation);
-        return;
+        // Overwrite previous $set value if present
+        BOOL shouldOverwriteProperty = NO;
+        if ([operation isEqualToString:AMP_OP_SET]) {
+            NSMutableDictionary *setOperations = [_userPropertyOperations objectForKey:AMP_OP_SET];
+            if (setOperations[property] != nil) {
+                shouldOverwriteProperty = YES;
+            }
+        }
+
+        if (shouldOverwriteProperty == NO) {
+            AMPLITUDE_LOG(@"Already used property '%@' in previous operation, ignoring for operation '%@'", property, operation);
+            return;
+        }
     }
 
     NSMutableDictionary *operations = [_userPropertyOperations objectForKey:operation];

Sources/Amplitude/AMPURLSession.h

@@ -29,6 +29,7 @@
 @interface AMPURLSession : ISPPinnedNSURLSessionDelegate <NSURLSessionDelegate, NSURLSessionTaskDelegate, NSURLSessionDataDelegate>
 
 + (AMPURLSession *)sharedSession;
+- (instancetype)initWithConfiguration:(NSURLSessionConfiguration *)configuration;
 - (NSURLSessionDataTask *)dataTaskWithRequest:(NSURLRequest *)request completionHandler:(void (^)(NSData *data, NSURLResponse *response, NSError *error))completionHandler;
 
 @end

Sources/Amplitude/AMPURLSession.m

@@ -58,9 +58,12 @@ + (AMPURLSession *)sharedSession {
 }
 
 - (instancetype)init {
+    return [self initWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]];
+}
+
+- (instancetype)initWithConfiguration:(NSURLSessionConfiguration *)configuration {
     if ((self = [super init])) {
         [AMPURLSession pinSSLCertificate:@[@"ComodoRsaDomainValidationCA"]];
-        NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
         _sharedSession = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:nil];
     }
     return self;

Sources/Amplitude/Amplitude.m

@@ -87,6 +87,7 @@ @interface Amplitude ()
 
 @property (nonatomic, strong) NSOperationQueue *backgroundQueue;
 @property (nonatomic, strong) NSOperationQueue *initializerQueue;
+@property (nonatomic, strong) id urlSession;
 @property (nonatomic, strong) AMPDatabaseHelper *dbHelper;
 @property (nonatomic, assign) BOOL initialized;
 @property (nonatomic, assign) BOOL sslPinningEnabled;
@@ -137,6 +138,7 @@ @implementation Amplitude {
 
     BOOL _inForeground;
     BOOL _offline;
+    BOOL _sendOverInexpensiveNetworkOnly;
 
     NSString *_serverUrl;
     NSString *_token;
@@ -204,6 +206,7 @@ - (instancetype)initWithInstanceName:(NSString *)instanceName {
         _useAdvertisingIdForDeviceId = NO;
         _backoffUpload = NO;
         _offline = NO;
+        _sendOverInexpensiveNetworkOnly = NO;
         _serverUrl = kAMPEventLogUrl;
         _serverZone = US;
         self.libraryName = kAMPLibrary;
@@ -991,13 +994,30 @@ - (void)makeEventUploadPostRequest:(NSString *)url events:(NSString *)events num
     [request setHTTPBody:postData];
     AMPLITUDE_LOG(@"Events: %@", events);
 
-    // If pinning is enabled, use the AMPURLSession that handles it.
+    // Configure the appropriate URL session
+    if (self.urlSession == nil) {
+        NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
+        if (self->_sendOverInexpensiveNetworkOnly) {
+            configuration.allowsCellularAccess = NO;
+            if (@available(iOS 13.0, *)) {
+                configuration.allowsExpensiveNetworkAccess = NO;
+                configuration.allowsConstrainedNetworkAccess = NO;
+            }
+        }
+
+        if (self.sslPinningEnabled) {
+            // If pinning is enabled, use the AMPURLSession that handles it.
 #if AMPLITUDE_SSL_PINNING
-    id session = (self.sslPinningEnabled ? [AMPURLSession class] : [NSURLSession class]);
-#else
-    id session = [NSURLSession class];
+            self.urlSession = [[AMPURLSession alloc] initWithConfiguration:configuration];
 #endif
-    [[[session sharedSession] dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
+        } else {
+            self.urlSession = [NSURLSession sessionWithConfiguration:configuration delegate:nil delegateQueue:nil];
+        }
+    }
+
+    id session = self.urlSession;
+
+    [[session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
         BOOL uploadSuccessful = NO;
         NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;
         if (response != nil) {
@@ -1425,6 +1445,14 @@ - (void)setOffline:(BOOL)offline {
     }
 }
 
+- (void)setSendOverInexpensiveNetworkOnly:(BOOL)sendOverInexpensiveNetworkOnly {
+    if (_sendOverInexpensiveNetworkOnly != sendOverInexpensiveNetworkOnly) {
+        _sendOverInexpensiveNetworkOnly = sendOverInexpensiveNetworkOnly;
+        self.urlSession = nil;
+    }
+}
+
+
 - (void)setServerUrl:(NSString *)serverUrl {
     if (!(serverUrl == nil || [self isArgument:serverUrl validType:[NSString class] methodName:@"setServerUrl:"])) {
         return;

Sources/Amplitude/Public/Amplitude.h

@@ -606,6 +606,15 @@ typedef void (^AMPInitCompletionBlock)(void);
  */
 - (void)setOffline:(BOOL)offline;
 
+/**
+ Use only non-cellular, inexpensive and non-constrained network for sending of logged events to Amplitude servers.
+
+ Setting this to YES would prevent the use of expensive network for sending logged events to Amplitude servers. Expensive network includes cellular network, and in iOS 13 and later—personal hotspot and any network explicitly marked by user for low data use.
+
+ @param sendOverInexpensiveNetworkOnly          Whether logged events should be sent over inexpensive network only
+ */
+- (void)setSendOverInexpensiveNetworkOnly:(BOOL)sendOverInexpensiveNetworkOnly;
+
 /**
  Uses advertisingIdentifier instead of identifierForVendor as the device ID