com.nineoldandroids.util.Property Maven / Gradle / Ivy
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/*
* Copyright (C) 2011 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.nineoldandroids.util;
/**
* A property is an abstraction that can be used to represent a mutable value that is held
* in a host object. The Property's {@link #set(Object, Object)} or {@link #get(Object)}
* methods can be implemented in terms of the private fields of the host object, or via "setter" and
* "getter" methods or by some other mechanism, as appropriate.
*
* @param The class on which the property is declared.
* @param The type that this property represents.
*/
public abstract class Property {
private final String mName;
private final Class mType;
/**
* This factory method creates and returns a Property given the class and
* name parameters, where the "name" parameter represents either:
*
* - a public
getName() method on the class which takes no arguments, plus an
* optional public setName() method which takes a value of the same type
* returned by getName()
* - a public
isName() method on the class which takes no arguments, plus an
* optional public setName() method which takes a value of the same type
* returned by isName()
* - a public
name field on the class
*
*
* If either of the get/is method alternatives is found on the class, but an appropriate
* setName() method is not found, the Property will be
* {@link #isReadOnly() readOnly}. Calling the {@link #set(Object, Object)} method on such
* a property is allowed, but will have no effect.
*
* If neither the methods nor the field are found on the class a
* {@link NoSuchPropertyException} exception will be thrown.
*/
public static Property of(Class hostType, Class valueType, String name) {
return new ReflectiveProperty(hostType, valueType, name);
}
/**
* A constructor that takes an identifying name and {@link #getType() type} for the property.
*/
public Property(Class type, String name) {
mName = name;
mType = type;
}
/**
* Returns true if the {@link #set(Object, Object)} method does not set the value on the target
* object (in which case the {@link #set(Object, Object) set()} method should throw a {@link
* NoSuchPropertyException} exception). This may happen if the Property wraps functionality that
* allows querying the underlying value but not setting it. For example, the {@link #of(Class,
* Class, String)} factory method may return a Property with name "foo" for an object that has
* only a getFoo() or isFoo() method, but no matching
* setFoo() method.
*/
public boolean isReadOnly() {
return false;
}
/**
* Sets the value on object which this property represents. If the method is unable
* to set the value on the target object it will throw an {@link UnsupportedOperationException}
* exception.
*/
public void set(T object, V value) {
throw new UnsupportedOperationException("Property " + getName() +" is read-only");
}
/**
* Returns the current value that this property represents on the given object.
*/
public abstract V get(T object);
/**
* Returns the name for this property.
*/
public String getName() {
return mName;
}
/**
* Returns the type for this property.
*/
public Class getType() {
return mType;
}
}