feat: add signature library missing check

Author: nonelse

Adjust/Adjust.m

@@ -319,6 +319,10 @@ + (void)setTestOptions:(NSDictionary *)testOptions {
 #pragma mark - Public instance methods
 
 - (void)initSdk:(ADJConfig *)adjustConfig {
+    if (! [self isSignerPresent]) {
+        [self.logger error:@"Missing signature library, SDK can't be initialised"];
+        return;
+    }
     if (self.activityHandler != nil) {
         [self.logger error:@"Adjust already initialized"];
         return;
@@ -327,6 +331,15 @@ - (void)initSdk:(ADJConfig *)adjustConfig {
                                                        savedPreLaunch:self.savedPreLaunch
                                            deeplinkResolutionCallback:self.cachedResolvedDeeplinkBlock];
 }
+- (BOOL)isSignerPresent {
+    _Nullable Class signerClass = NSClassFromString(@"ADJSigner");
+    if (signerClass == nil) {
+        return NO;
+    }
+
+    return [signerClass respondsToSelector:
+            NSSelectorFromString(@"sign:withExtraParams:withOutputParams:")];
+}
 
 - (void)trackEvent:(ADJEvent *)event {
     if (![self checkActivityHandler]) {