Add method to check if a key has a value

Author: hzalaz

Example/Tests/A0SimpleKeychainSpec.m

@@ -170,6 +170,18 @@
             [keychain setString:@"value1" forKey:key];
         });
 
+        it(@"should return that a nonexisting key doesnt exist", ^{
+            expect([keychain stringForKey:@"SHOULDNOTEXIST"]).to.beFalsy();
+        });
+
+        it(@"should return that a nil key doesnt exist", ^{
+            expect([keychain stringForKey:nil]).to.beFalsy();
+        });
+
+        it(@"should return that a key exists", ^{
+            expect([keychain stringForKey:key]).to.beTruthy();
+        });
+
         it(@"should return nil string with nil key", ^{
             expect([keychain stringForKey:nil]).to.beNil();
         });

Pod/Classes/A0SimpleKeychain.h

@@ -219,6 +219,15 @@ typedef NS_ENUM(NSInteger, A0SimpleKeychainItemAccessible) {
  */
 - (NSData *)dataForKey:(NSString *)key promptMessage:(NSString *)message;
 
+/**
+ *  Checks if a key has a value in the Keychain
+ *
+ *  @param key the key to check if it has a value
+ *
+ *  @return if the key has an associated value in the Keychain or not.
+ */
+- (BOOL)hasValueForKey:(NSString *)key;
+
 ///---------------------------------------------------
 /// @name Create helper methods
 ///---------------------------------------------------

Pod/Classes/A0SimpleKeychain.m

@@ -85,6 +85,15 @@ - (NSData *)dataForKey:(NSString *)key promptMessage:(NSString *)message {
     return dataFound;
 }
 
+- (BOOL)hasValueForKey:(NSString *)key {
+    if (key) {
+        return NO;
+    }
+    NSDictionary *query = [self queryFindByKey:key message:nil];
+    OSStatus status = SecItemCopyMatching((__bridge CFDictionaryRef)query, NULL);
+    return status == errSecSuccess;
+}
+
 - (BOOL)setString:(NSString *)string forKey:(NSString *)key {
     return [self setString:string forKey:key promptMessage:nil];
 }