add method to enable feature flags from server (#196)

Author: e7mac

Leanplum-SDK/Classes/Internal/FeatureFlag/LPFeatureFlagManager.h

@@ -10,6 +10,8 @@
 @interface LPFeatureFlagManager : NSObject
 
 + (instancetype)sharedManager;
--(BOOL)isFeatureFlagEnabled:(NSString *)featureFlagName;
+
+-(void)refreshEnabledFeatureFlags:(nullable NSArray<NSString *> *)featureFlags;
+-(BOOL)isFeatureFlagEnabled:(nonnull NSString *)featureFlagName;
 
 @end

Leanplum-SDK/Classes/Internal/FeatureFlag/LPFeatureFlagManager.m

@@ -7,6 +7,12 @@
 
 #import "LPFeatureFlagManager.h"
 
+@interface LPFeatureFlagManager()
+
+@property (strong, nonatomic) NSSet *enabledFeatureFlags;
+
+@end
+
 @implementation LPFeatureFlagManager
 
 static LPFeatureFlagManager *sharedFeatureFlagManager = nil;
@@ -19,8 +25,14 @@ + (instancetype)sharedManager {
     return sharedFeatureFlagManager;
 }
 
--(BOOL)isFeatureFlagEnabled:(NSString *)featureFlagName {
-    return NO;
+-(void)refreshEnabledFeatureFlags:(nullable NSArray<NSString *> *)featureFlags {
+    if (featureFlags != nil) {
+        self.enabledFeatureFlags = [NSSet setWithArray:featureFlags];
+    }
+}
+
+-(BOOL)isFeatureFlagEnabled:(nonnull NSString *)featureFlagName {
+    return [self.enabledFeatureFlags containsObject:featureFlagName];
 }
 
 @end