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Equals() should be type safe, null-aware and hashcode() should be overridden #104

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Mar 24, 2014
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Equals() should be type safe, null-aware and hashcode() should be overridden #104

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7de4a28
Typesafe equals, null-aware equals, implemented hashcode.
vsigler Aug 10, 2013
056032a
Merge branch 'master' of https://github.com/vsigler/ActiveAndroid.git
vsigler Aug 10, 2013
c5e4d89
When not in db (id null), Model instance is equal only to itself.
vsigler Aug 10, 2013
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22 changes: 19 additions & 3 deletions src/com/activeandroid/Model.java
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,10 @@

@SuppressWarnings("unchecked")
public abstract class Model {

/** Prime number used for hashcode() implementation. */
private static final int HASH_PRIME = 739;

//////////////////////////////////////////////////////////////////////////////////////
// PRIVATE MEMBERS
//////////////////////////////////////////////////////////////////////////////////////
Expand Down Expand Up @@ -287,9 +291,21 @@ public String toString() {

@Override
public boolean equals(Object obj) {
final Model other = (Model) obj;
if (obj instanceof Model && this.mId != null) {
final Model other = (Model) obj;

return this.mId.equals(other.mId)
&& (this.mTableInfo.getTableName().equals(other.mTableInfo.getTableName()));
} else {
return this == obj;
}
}

return this.mId != null && (this.mTableInfo.getTableName().equals(other.mTableInfo.getTableName()))
&& (this.mId.equals(other.mId));
@Override
public int hashCode() {
int hash = HASH_PRIME;
hash += HASH_PRIME * (mId == null ? super.hashCode() : mId.hashCode()); //if id is null, use Object.hashCode()
hash += HASH_PRIME * mTableInfo.getTableName().hashCode();
return hash; //To change body of generated methods, choose Tools | Templates.
}
}
129 changes: 129 additions & 0 deletions tests/src/com/activeandroid/test/ModelTest.java
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Original file line number Diff line number Diff line change
@@ -0,0 +1,129 @@
/*
* Copyright (C) 2013 Vojtech Sigler.
*
* 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.activeandroid.test;

import com.activeandroid.Model;
import com.activeandroid.annotation.Table;
import java.util.HashSet;
import java.util.Set;
import static junit.framework.Assert.assertEquals;
import static junit.framework.Assert.assertFalse;

/**
* Simple test now covering equals and hashcode methods.
*/
public class ModelTest extends ActiveAndroidTestCase {

/**
* Equals should be type-safe.
*/
public void testEqualsNonModel() {
MockModel model = new MockModel();

assertFalse(model.equals("Dummy"));
assertFalse(model.equals(null));
}

/**
* Equals should not be true for different model classes.
*/
public void testEqualsDifferentModel() {
Model model1 = new MockModel();
Model model2 = new AnotherMockModel();

assertFalse(model1.equals(model2));
}

/**
* A new object does not have PK assigned yet,
* therefore by default it is equal only to itself.
*/
public void testEqualsOnNew() {
MockModel model1 = new MockModel();
MockModel model2 = new MockModel();

assertFalse(model1.equals(model2));
assertFalse(model2.equals(model1));
assertTrue(model1.equals(model1));//equal only to itself
}

/**
* Two different rows in a table should not be equal (different ids).
*/
public void testEqualsDifferentRows() {
MockModel model1 = new MockModel();
MockModel model2 = new MockModel();
MockModel model3;

model1.save();
model2.save();
model3 = Model.load(MockModel.class, model1.getId());

assertFalse(model1.equals(model2));
assertFalse(model2.equals(model1));
assertTrue(model1.equals(model3));
assertTrue(model1.equals(model3));
assertFalse(model3.equals(model2));
assertFalse(model2.equals(model3));
}

/**
* Tests hashcode for new instances.
*/
public void testHashCode() {
Set<Model> set = new HashSet<Model>();
Model m1 = new MockModel();
Model m2 = new MockModel();
Model m3 = new AnotherMockModel();

assertFalse(m1.hashCode() == m2.hashCode()); // hashes for unsaved models must not match
set.add(m1);
set.add(m2);
assertEquals(2, set.size()); //try in a set

assertFalse(m1.hashCode() == m3.hashCode());
set.add(m3);
assertEquals(3, set.size());
}

/**
* Two rows in a table should have different hashcodes.
*/
public void testHashCodeDifferentRows() {
Set<Model> set = new HashSet<Model>();
Model m1 = new MockModel();
Model m2 = new MockModel();
Model m3;

m1.save();
m2.save();
m3 = Model.load(MockModel.class, m1.getId());

assertEquals(m1.hashCode(), m3.hashCode());
assertFalse(m1.hashCode() == m2.hashCode());
set.add(m1);
set.add(m2);
set.add(m3);
assertEquals(2, set.size());
}

/**
* Mock model as we need 2 different model classes.
*/
@Table(name = "AnotherMockTable")
public static class AnotherMockModel extends Model {}
}