Feature kotlin delegates (#892)

* Implement generic delegate for attributes

Signed-off-by: Daniel San <[email protected]>

* Implement specialized property delegation for boolean

Signed-off-by: Daniel San <[email protected]>

* Implement specialized property delegation for double

Signed-off-by: Daniel San <[email protected]>

* Implement specialized property delegation for float

Signed-off-by: Daniel San <[email protected]>

* Implement specialized property delegation for int

Signed-off-by: Daniel San <[email protected]>

* Implement specialized property delegation for long

Signed-off-by: Daniel San <[email protected]>

* Implement specialized property delegation for string

Signed-off-by: Daniel San <[email protected]>

* Implement specialized property delegation for bytes

Signed-off-by: Daniel San <[email protected]>

* Implement specialized property delegation for map

Signed-off-by: Daniel San <[email protected]>

* Implement specialized property delegation for list

Signed-off-by: Daniel San <[email protected]>

* Implement specialized property delegation for JsonArray

Signed-off-by: Daniel San <[email protected]>

* Implement specialized property delegation for JsonObject

Signed-off-by: Daniel San <[email protected]>

* Implement specialized property delegation for ParseRelation

Signed-off-by: Daniel San <[email protected]>

* Implement specialized property delegation for Enum

Signed-off-by: Daniel San <[email protected]>

* Implement generic delegate for attributes with some checks

Signed-off-by: Daniel San <[email protected]>

* Small fix on ParseDelegate set property type

Signed-off-by: Daniel San <[email protected]>

* Add basic documentation to all delegate classes

Signed-off-by: Daniel San <[email protected]>

* Add property delegation documentation on README.md

Signed-off-by: Daniel San <[email protected]>

* Update kotlin version

Signed-off-by: Daniel San <[email protected]>

Author: danielsanfr

build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.2.51'
+    ext.kotlin_version = '1.2.71'
     repositories {
         jcenter()
         google()

ktx/README.md

@@ -37,6 +37,44 @@ class Cat : ParseObject() {
 
 ```
 
+## Property Delegation
+
+> "There are certain common kinds of properties, that, though we can implement them manually every time we need them, would be very nice to implement once and for all, and put into a library."
+
+The text quoted above is the best explanation anyone could pass us, we use property delegation for the properties of our ParseObject, this prevents us having to write very much boilerplate.
+
+### Without property delegation:
+
+```kotlin
+@ParseClassName("Cat")
+class Cat : ParseObject() {
+
+    companion object {
+        const val KEY_NAME = "name"
+    }
+
+    var name: String
+        get = getString(KEY_NAME)
+        set(value) = putString(KEY_NAME, value)
+
+}
+```
+
+### With property delegation:
+
+```kotlin
+@ParseClassName("Cat")
+class Cat : ParseObject() {
+
+    var name: String by stringAttribute() // That's it
+
+}
+```
+
+The `stringAttribute` is a property delegate, and we have many other specialized types and also for generic types.
+
+This causes us to not have to write get/set and besides, it removed the get/put boilerplate which is a must to map our classes with the Parse collections.
+
 ## Contributing
 When contributing to the `ktx` module, please first consider if the extension function you are wanting to add would potentially be better suited in the main `parse` module. If it is something specific to Kotlin users or only useful in a Kotlin project, feel free to make a PR adding it to this module. Otherwise, consider adding the addition to the `parse` module itself, so that it is still usable in Java.
 

ktx/src/main/java/com/parse/ktx/delegates/BooleanParseDelegate.kt

@@ -0,0 +1,27 @@
+@file:Suppress("unused", "NOTHING_TO_INLINE")
+
+package com.parse.ktx.delegates
+
+import com.parse.ParseObject
+import kotlin.reflect.KProperty
+
+/**
+ * A [Boolean] property delegation for [ParseObject].
+ */
+class BooleanParseDelegate {
+
+    operator fun getValue(parseObject: ParseObject, property: KProperty<*>): Boolean {
+        return parseObject.getBoolean(property.name)
+    }
+
+    operator fun setValue(parseObject: ParseObject, property: KProperty<*>, value: Boolean) {
+        parseObject.put(property.name, value)
+    }
+
+}
+
+/**
+ * Returns a [Boolean] property delegate for [ParseObject]s. This uses [ParseObject.getBoolean]
+ * and [ParseObject.put].
+ */
+inline fun booleanAttribute() = BooleanParseDelegate()

ktx/src/main/java/com/parse/ktx/delegates/BytesParseDelegate.kt

@@ -0,0 +1,28 @@
+@file:Suppress("unused", "NOTHING_TO_INLINE")
+
+package com.parse.ktx.delegates
+
+import com.parse.ParseObject
+import com.parse.ktx.putOrIgnore
+import kotlin.reflect.KProperty
+
+/**
+ * A [ByteArray] property delegation for [ParseObject].
+ */
+class BytesParseDelegate {
+
+    operator fun getValue(parseObject: ParseObject, property: KProperty<*>): ByteArray? {
+        return parseObject.getBytes(property.name)
+    }
+
+    operator fun setValue(parseObject: ParseObject, property: KProperty<*>, value: ByteArray?) {
+        parseObject.putOrIgnore(property.name, value)
+    }
+
+}
+
+/**
+ * Returns a [ByteArray] property delegate for [ParseObject]s. This uses [ParseObject.getBytes]
+ * and [ParseObject.putOrIgnore].
+ */
+inline fun bytesAttribute() = BytesParseDelegate()

ktx/src/main/java/com/parse/ktx/delegates/DoubleParseDelegate.kt

@@ -0,0 +1,27 @@
+@file:Suppress("unused", "NOTHING_TO_INLINE")
+
+package com.parse.ktx.delegates
+
+import com.parse.ParseObject
+import kotlin.reflect.KProperty
+
+/**
+ * A [Double] property delegation for [ParseObject].
+ */
+class DoubleParseDelegate {
+
+    operator fun getValue(parseObject: ParseObject, property: KProperty<*>): Double {
+        return parseObject.getDouble(property.name)
+    }
+
+    operator fun setValue(parseObject: ParseObject, property: KProperty<*>, value: Double) {
+        parseObject.put(property.name, value)
+    }
+
+}
+
+/**
+ * Returns a [Double] property delegate for [ParseObject]s. This uses [ParseObject.getDouble]
+ * and [ParseObject.put].
+ */
+inline fun doubleAttribute() = DoubleParseDelegate()

ktx/src/main/java/com/parse/ktx/delegates/EnumParseDelegate.kt

@@ -0,0 +1,34 @@
+@file:Suppress("unused")
+
+package com.parse.ktx.delegates
+
+import com.parse.ParseObject
+import kotlin.reflect.KProperty
+
+/**
+ * A [Enum] property delegation for [ParseObject].
+ *
+ * This implementation save enum's name in lower case on parse-server and when try retrieve it
+ * convert again to upper case to find correspondent local enum.
+ */
+class EnumParseDelegate<T : Enum<T>>(private val default: T?, private val enumClass: Class<T>) {
+
+    operator fun getValue(parseObject: ParseObject, property: KProperty<*>): T {
+        return try {
+            java.lang.Enum.valueOf(enumClass, parseObject.getString(property.name)!!.toUpperCase())
+        } catch (e: Exception) {
+            default ?: throw e
+        }
+    }
+
+    operator fun setValue(parseObject: ParseObject, property: KProperty<*>, t: T) {
+        parseObject.put(property.name, t.name.toLowerCase())
+    }
+
+}
+
+/**
+ * Returns a [Enum] property delegate for [ParseObject]s. This uses custom implementation for get
+ * to retrieve a local version of the your enum and [ParseObject.put].
+ */
+inline fun <reified T : Enum<T>> enumAttribute(default: T? = null) = EnumParseDelegate(default, T::class.java)

ktx/src/main/java/com/parse/ktx/delegates/FloatParseDelegate.kt

@@ -0,0 +1,27 @@
+@file:Suppress("unused", "NOTHING_TO_INLINE")
+
+package com.parse.ktx.delegates
+
+import com.parse.ParseObject
+import kotlin.reflect.KProperty
+
+/**
+ * A [Float] property delegation for [ParseObject].
+ */
+class FloatParseDelegate {
+
+    operator fun getValue(parseObject: ParseObject, property: KProperty<*>): Float {
+        return parseObject.getDouble(property.name).toFloat()
+    }
+
+    operator fun setValue(parseObject: ParseObject, property: KProperty<*>, value: Float) {
+        parseObject.put(property.name, value)
+    }
+
+}
+
+/**
+ * Returns a [Float] property delegate for [ParseObject]s. This uses a custom implementation for get
+ * and [ParseObject.put].
+ */
+inline fun floatAttribute() = FloatParseDelegate()

ktx/src/main/java/com/parse/ktx/delegates/IntParseDelegate.kt

@@ -0,0 +1,27 @@
+@file:Suppress("unused", "NOTHING_TO_INLINE")
+
+package com.parse.ktx.delegates
+
+import com.parse.ParseObject
+import kotlin.reflect.KProperty
+
+/**
+ * A [Int] property delegation for [ParseObject].
+ */
+class IntParseDelegate {
+
+    operator fun getValue(parseObject: ParseObject, property: KProperty<*>): Int {
+        return parseObject.getInt(property.name)
+    }
+
+    operator fun setValue(parseObject: ParseObject, property: KProperty<*>, value: Int) {
+        parseObject.put(property.name, value)
+    }
+
+}
+
+/**
+ * Returns a [Int] property delegate for [ParseObject]s. This uses [ParseObject.getInt]
+ * and [ParseObject.put].
+ */
+inline fun intAttribute() = IntParseDelegate()

ktx/src/main/java/com/parse/ktx/delegates/JsonArrayParseDelegate.kt

@@ -0,0 +1,29 @@
+@file:Suppress("unused", "NOTHING_TO_INLINE")
+
+package com.parse.ktx.delegates
+
+import com.parse.ParseObject
+import com.parse.ktx.putOrIgnore
+import org.json.JSONArray
+import kotlin.reflect.KProperty
+
+/**
+ * A [JSONArray] property delegation for [ParseObject].
+ */
+class JsonArrayParseDelegate {
+
+    operator fun getValue(parseObject: ParseObject, property: KProperty<*>): JSONArray? {
+        return parseObject.getJSONArray(property.name)
+    }
+
+    operator fun setValue(parseObject: ParseObject, property: KProperty<*>, value: JSONArray?) {
+        parseObject.putOrIgnore(property.name, value)
+    }
+
+}
+
+/**
+ * Returns a [JSONArray] property delegate for [ParseObject]s. This uses [ParseObject.getDouble]
+ * and [ParseObject.putOrIgnore].
+ */
+inline fun jsonArrayAttribute() = JsonArrayParseDelegate()

ktx/src/main/java/com/parse/ktx/delegates/JsonObjectParseDelegate.kt

@@ -0,0 +1,29 @@
+@file:Suppress("unused", "NOTHING_TO_INLINE")
+
+package com.parse.ktx.delegates
+
+import com.parse.ParseObject
+import com.parse.ktx.putOrIgnore
+import org.json.JSONObject
+import kotlin.reflect.KProperty
+
+/**
+ * A [JSONObject] property delegation for [ParseObject].
+ */
+class JsonObjectParseDelegate {
+
+    operator fun getValue(parseObject: ParseObject, property: KProperty<*>): JSONObject? {
+        return parseObject.getJSONObject(property.name)
+    }
+
+    operator fun setValue(parseObject: ParseObject, property: KProperty<*>, value: JSONObject?) {
+        parseObject.putOrIgnore(property.name, value)
+    }
+
+}
+
+/**
+ * Returns a [JSONObject] property delegate for [ParseObject]s. This uses [ParseObject.getJSONObject]
+ * and [ParseObject.putOrIgnore].
+ */
+fun jsonObjectAttribute() = JsonObjectParseDelegate()