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Sources/JNI/JNIFields.swift

@@ -7,23 +7,19 @@
 
 import CJNI
 
-struct FieldIDNotFound: Error {}
-
 public extension JNI {
      public func GetStaticField<T: JavaParameterConvertible>(_ fieldName: String, on javaClass: JavaClass) throws -> T {
         let env = self._env
-        guard let fieldID = env.pointee.pointee.GetStaticFieldID(env, javaClass, fieldName, T.asJNIParameterString) else {
-            throw FieldIDNotFound()
-        }
-        return try T.fromStaticField(of: javaClass, id: fieldID)
+        let fieldID = env.pointee.pointee.GetStaticFieldID(env, javaClass, fieldName, T.asJNIParameterString)
+        try checkAndThrowOnJNIError()
+        return try T.fromStaticField(of: javaClass, id: fieldID!)
     }
 
     public func GetField<T: JavaParameterConvertible>(_ fieldName: String, from javaObject: JavaObject) throws -> T {
         let env = self._env
-        guard let javaClass = GetObjectClass(obj: javaObject),
-              let fieldID = env.pointee.pointee.GetFieldID(env, javaClass, fieldName, T.asJNIParameterString) else {
-            throw FieldIDNotFound()
-        }
-        return try T.fromField(of: javaObject, id: fieldID)
+        let javaClass = try GetObjectClass(obj: javaObject)
+        let fieldID = env.pointee.pointee.GetFieldID(env, javaClass, fieldName, T.asJNIParameterString)
+        try checkAndThrowOnJNIError()
+        return try T.fromField(of: javaObject, id: fieldID!)
     }
 }

Sources/JNI/JNIObjects.swift

@@ -1,7 +1,6 @@
 import CJNI
 
 struct CreateNewObjectForConstructorError: Error {}
-struct ClassNotFound: Error {}
 struct ConstructorError: Error {}
 
 /// Designed to simplify calling a constructor and methods on a JavaClass
@@ -13,18 +12,16 @@ open class JNIObject {
     public init(_ className: String, arguments: [JavaParameterConvertible] = []) throws {
         let className = className.replacingFullstopsWithSlashes()
 
-        guard
-            let javaClassLocalRef = jni.FindClass(name: className),
-            let javaClass = jni.NewGlobalRef(javaClassLocalRef)
-        else {
-            assertionFailure("Couldn't find class named \(className)")
-            throw ClassNotFound()
-        }
+        let javaClassLocalRef = jni.FindClass(name: className)
+        try checkAndThrowOnJNIError()
 
-        self.javaClass = javaClass
+        let javaClass = jni.NewGlobalRef(javaClassLocalRef!)
+        try checkAndThrowOnJNIError()
+
+        self.javaClass = javaClass!
 
         guard
-            let instanceLocalRef = try? jni.callConstructor(on: javaClass, arguments: arguments),
+            let instanceLocalRef = try? jni.callConstructor(on: self.javaClass, arguments: arguments),
             let instance = jni.NewGlobalRef(instanceLocalRef)
         else {
             assertionFailure("Error during call to constructor of \(className)")
@@ -72,10 +69,11 @@ public extension JNI {
         return newObject
 	}
 
-	public func GetObjectClass(obj: JavaObject) -> JavaClass? {
+	public func GetObjectClass(obj: JavaObject) throws -> JavaClass {
 	    let env = self._env
         let result = env.pointee.pointee.GetObjectClass(env, obj)
-        return (result != nil) ? result : .none
+        try checkAndThrowOnJNIError()
+        return result!
 	}
 
 }

Sources/JNI/JavaParameterConvertible.swift

@@ -38,7 +38,7 @@ extension Bool: JavaParameterConvertible {
     }
 
     public static func fromField(of javaObject: JavaObject, id: jfieldID) throws -> Bool {
-        return jni.GetBooleanField(of: javaObject, id: id) == 1
+        return try jni.GetBooleanField(of: javaObject, id: id) == JNI_TRUE
     }
 }
 
@@ -65,7 +65,7 @@ extension Int: JavaParameterConvertible {
     }
 
     public static func fromField(of javaObject: JavaObject, id: jfieldID) throws -> Int {
-        return Int(jni.GetIntField(of: javaObject, id: id))
+        return try Int(jni.GetIntField(of: javaObject, id: id))
     }
 }
 
@@ -77,8 +77,7 @@ extension Double: JavaParameterConvertible {
     }
 
     public static func fromStaticField(of javaClass: JavaClass, id: jfieldID) throws -> Double {
-        let result = try jni.GetStaticDoubleField(of: javaClass, id: id)
-        return Double(result)
+        return try Double(jni.GetStaticDoubleField(of: javaClass, id: id))
     }
 
     public static func fromMethod(calling methodID: JavaMethodID, on object: JavaObject, args: [JavaParameter]) throws -> Double {
@@ -90,7 +89,7 @@ extension Double: JavaParameterConvertible {
     }
 
     public static func fromField(of javaObject: JavaObject, id: jfieldID) throws -> Double {
-        return Double(jni.GetDoubleField(of: javaObject, id: id))
+        return try jni.GetDoubleField(of: javaObject, id: id)
     }
 }
 
@@ -119,9 +118,7 @@ extension String: JavaParameterConvertible {
     }
 
     public static func fromField(of javaObject: JavaObject, id: jfieldID) throws -> String {
-        guard let javaStringObject = jni.GetObjectField(of: javaObject, id: id) else {
-            throw FieldIDNotFound()
-        }
+        let javaStringObject = try jni.GetObjectField(of: javaObject, id: id)
         return jni.GetString(from: javaStringObject)
     }
 }

Sources/JNI/SwiftJNI.swift

@@ -56,12 +56,10 @@ extension JNI {
         let objectClass = _env.pointee.pointee.GetObjectClass(_env, object)
         try checkAndThrowOnJNIError()
 
-        guard let result = _env.pointee.pointee.GetMethodID(_env, objectClass!, methodName, methodSignature) else {
-            throw InvalidMethodID()
-        }
-
+        let result = _env.pointee.pointee.GetMethodID(_env, objectClass!, methodName, methodSignature)
         try checkAndThrowOnJNIError()
-        return result
+
+        return result!
     }
 
     public func GetStaticMethodID(for javaClass: JavaClass, methodName: String, methodSignature: String) throws -> JavaMethodID {
@@ -164,24 +162,32 @@ extension JNI {
 
     // MARK: Fields
 
-    public func GetBooleanField(of javaObject: JavaObject, id: jfieldID) -> JavaBoolean {
+    public func GetBooleanField(of javaObject: JavaObject, id: jfieldID) throws -> JavaBoolean {
         let _env = self._env
-        return _env.pointee.pointee.GetBooleanField(_env, javaObject, id)
+        let result = _env.pointee.pointee.GetBooleanField(_env, javaObject, id)
+        try checkAndThrowOnJNIError()
+        return result
     }
 
-    public func GetIntField(of javaObject: JavaObject, id: jfieldID) -> JavaInt {
+    public func GetIntField(of javaObject: JavaObject, id: jfieldID) throws -> JavaInt {
         let _env = self._env
-        return _env.pointee.pointee.GetIntField(_env, javaObject, id)
+        let result = _env.pointee.pointee.GetIntField(_env, javaObject, id)
+        try checkAndThrowOnJNIError()
+        return result
     }
 
-    public func GetDoubleField(of javaObject: JavaObject, id: jfieldID) -> JavaDouble {
+    public func GetDoubleField(of javaObject: JavaObject, id: jfieldID) throws -> JavaDouble {
         let _env = self._env
-        return _env.pointee.pointee.GetDoubleField(_env, javaObject, id)
+        let result = _env.pointee.pointee.GetDoubleField(_env, javaObject, id)
+        try checkAndThrowOnJNIError()
+        return result
     }
 
-    public func GetObjectField(of javaObject: JavaObject, id: jfieldID) -> JavaObject? {
+    public func GetObjectField(of javaObject: JavaObject, id: jfieldID) throws -> JavaObject {
         let _env = self._env
-        return _env.pointee.pointee.GetObjectField(_env, javaObject, id)
+        let result = _env.pointee.pointee.GetObjectField(_env, javaObject, id)
+        try checkAndThrowOnJNIError()
+        return result!
     }
 
     // MARK: Static Fields
@@ -315,9 +321,9 @@ extension JNI {
         if (index >= count) {
             throw JNIError()
         }
-        let jObj = _env.pointee.pointee.GetObjectArrayElement(_env, array, jsize(index))!
+        let jObj = _env.pointee.pointee.GetObjectArrayElement(_env, array, jsize(index))
         try checkAndThrowOnJNIError()
-        return jObj
+        return jObj!
     }
 }
 
@@ -381,7 +387,7 @@ public struct JavaCallback {
     - parameters: Any number of JavaParameters (*must have the same number and type as the* `methodSignature` *you're trying to call*)
     - Throws: `JavaCallback.Error`
     */
-    public init (_ globalJobj: JavaObject, methodName: String, methodSignature: String) {
+    public init (_ globalJobj: JavaObject, methodName: String, methodSignature: String) throws {
         // At the moment we can only call Void methods, fail if user tries to return something else
         guard let returnType = methodSignature.characters.last, returnType == "V"/*oid*/ else {
             // LOG JavaMethodCallError.IncorrectMethodSignature
@@ -393,10 +399,8 @@ public struct JavaCallback {
         // Doesn't work with more complex object types, arrays etc. we should determine the signature based on parameters.
 
         // TODO: Check methodSignature here and determine expectedParameterCount
-
-        guard
-            let javaClass = jni.GetObjectClass(obj: globalJobj),
-            let methodID = try? jni.GetMethodID(for: javaClass, methodName: methodName, methodSignature: methodSignature)
+        let javaClass = try jni.GetObjectClass(obj: globalJobj)
+        guard let methodID = try? jni.GetMethodID(for: javaClass, methodName: methodName, methodSignature: methodSignature)
             else {
                 // XXX: We should throw here and keep throwing til it gets back to Java
                 fatalError("Failed to make JavaCallback")