Allow string ids (#107)

airbnb · Feb 3, 2017 · cbfd18b · cbfd18b
1 parent c224a3b
commit cbfd18b
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diff --git a/epoxy-adapter/src/main/java/com/airbnb/epoxy/EpoxyModel.java b/epoxy-adapter/src/main/java/com/airbnb/epoxy/EpoxyModel.java
@@ -87,6 +87,76 @@ public EpoxyModel<T> id(long id) {
     return this;
   }
 
+  /**
+   * Use a string as the model id. Useful for models that don't clearly map to a numerical id. This
+   * is preferable to using {@link String#hashCode()} because that is a 32 bit hash and this is a 64
+   * bit hash, giving better spread and less chance of collision with other ids.
+   * <p>
+   * Since this uses a hashcode method to convert the String to a long there is a very small
+   * chance that you may have a collision with another id. Assuming an even spread of hashcodes, and
+   * several hundred models in the adapter, there would be roughly 1 in 100 trillion chance of a
+   * collision. (http://preshing.com/20110504/hash-collision-probabilities/)
+   *
+   * @see EpoxyModel#hashString64Bit(CharSequence)
+   */
+  public EpoxyModel<T> id(CharSequence key) {
+    id(hashString64Bit(key));
+    return this;
+  }
+
+  /**
+   * Set an id that is namespaced with a string. This is useful when you need to show models of
+   * multiple types, side by side and don't want to risk id collisions.
+   * <p>
+   * Since this uses a hashcode method to convert the String to a long there is a very small chance
+   * that you may have a collision with another id. Assuming an even spread of hashcodes, and
+   * several hundred models in the adapter, there would be roughly 1 in 100 trillion chance of a
+   * collision. (http://preshing.com/20110504/hash-collision-probabilities/)
+   *
+   * @see EpoxyModel#hashString64Bit(CharSequence)
+   * @see EpoxyModel#hashLong64Bit(long)
+   */
+  public EpoxyModel<T> id(CharSequence key, long id) {
+    long result = hashString64Bit(key);
+    result = 31 * result + hashLong64Bit(id);
+    id(result);
+    return this;
+  }
+
+  /**
+   * Hash a long into 64 bits instead of the normal 32. This uses a xor shift implementation to
+   * attempt psuedo randomness so object ids have an even spread for less chance of collisions.
+   * <p>
+   * From http://stackoverflow.com/a/11554034
+   * <p>
+   * http://www.javamex.com/tutorials/random_numbers/xorshift.shtml
+   */
+  private static long hashLong64Bit(long value) {
+    value ^= (value << 21);
+    value ^= (value >>> 35);
+    value ^= (value << 4);
+    return value;
+  }
+
+  /**
+   * Hash a string into 64 bits instead of the normal 32. This allows us to better use strings as a
+   * model id with less chance of collisions. This uses the FNV-1a algorithm for a good mix of speed
+   * and distribution.
+   * <p>
+   * Performance comparisons found at http://stackoverflow.com/a/1660613
+   * <p>
+   * Hash implementation from http://www.isthe.com/chongo/tech/comp/fnv/index.html#FNV-1a
+   */
+  private static long hashString64Bit(CharSequence str) {
+    long result = 0xcbf29ce484222325L;
+    final int len = str.length();
+    for (int i = 0; i < len; i++) {
+      result ^= str.charAt(i);
+      result *= 0x100000001b3L;
+    }
+    return result;
+  }
+
   @LayoutRes
   protected abstract int getDefaultLayout();
 

diff --git a/epoxy-processortest/src/test/resources/BasicModelWithAttribute_.java b/epoxy-processortest/src/test/resources/BasicModelWithAttribute_.java
@@ -1,6 +1,7 @@
 package com.airbnb.epoxy;
 
 import android.support.annotation.LayoutRes;
+import java.lang.CharSequence;
 import java.lang.Object;
 import java.lang.Override;
 import java.lang.String;
@@ -28,6 +29,18 @@ public BasicModelWithAttribute_ id(long id) {
     return this;
   }
 
+  @Override
+  public BasicModelWithAttribute_ id(CharSequence key) {
+    super.id(key);
+    return this;
+  }
+
+  @Override
+  public BasicModelWithAttribute_ id(CharSequence key, long id) {
+    super.id(key, id);
+    return this;
+  }
+
   @Override
   public BasicModelWithAttribute_ layout(@LayoutRes int arg0) {
     super.layout(arg0);

diff --git a/epoxy-processortest/src/test/resources/ModelReturningClassTypeWithVarargs_.java b/epoxy-processortest/src/test/resources/ModelReturningClassTypeWithVarargs_.java
@@ -1,6 +1,7 @@
 package com.airbnb.epoxy;
 
 import android.support.annotation.LayoutRes;
+import java.lang.CharSequence;
 import java.lang.Object;
 import java.lang.Override;
 import java.lang.String;
@@ -40,6 +41,18 @@ public ModelReturningClassTypeWithVarargs_ id(long id) {
     return this;
   }
 
+  @Override
+  public ModelReturningClassTypeWithVarargs_ id(CharSequence key) {
+    super.id(key);
+    return this;
+  }
+
+  @Override
+  public ModelReturningClassTypeWithVarargs_ id(CharSequence key, long id) {
+    super.id(key, id);
+    return this;
+  }
+
   @Override
   public ModelReturningClassTypeWithVarargs_ layout(@LayoutRes int arg0) {
     super.layout(arg0);

diff --git a/epoxy-processortest/src/test/resources/ModelReturningClassType_.java b/epoxy-processortest/src/test/resources/ModelReturningClassType_.java
@@ -1,6 +1,7 @@
 package com.airbnb.epoxy;
 
 import android.support.annotation.LayoutRes;
+import java.lang.CharSequence;
 import java.lang.Object;
 import java.lang.Override;
 import java.lang.String;
@@ -47,6 +48,18 @@ public ModelReturningClassType_ id(long id) {
     return this;
   }
 
+  @Override
+  public ModelReturningClassType_ id(CharSequence key) {
+    super.id(key);
+    return this;
+  }
+
+  @Override
+  public ModelReturningClassType_ id(CharSequence key, long id) {
+    super.id(key, id);
+    return this;
+  }
+
   @Override
   public ModelReturningClassType_ layout(@LayoutRes int arg0) {
     super.layout(arg0);

diff --git a/epoxy-processortest/src/test/resources/ModelWithAllFieldTypes_.java b/epoxy-processortest/src/test/resources/ModelWithAllFieldTypes_.java
@@ -3,6 +3,7 @@
 import android.support.annotation.LayoutRes;
 import java.lang.Boolean;
 import java.lang.Byte;
+import java.lang.CharSequence;
 import java.lang.Character;
 import java.lang.Double;
 import java.lang.Float;
@@ -217,6 +218,18 @@ public ModelWithAllFieldTypes_ id(long id) {
     return this;
   }
 
+  @Override
+  public ModelWithAllFieldTypes_ id(CharSequence key) {
+    super.id(key);
+    return this;
+  }
+
+  @Override
+  public ModelWithAllFieldTypes_ id(CharSequence key, long id) {
+    super.id(key, id);
+    return this;
+  }
+
   @Override
   public ModelWithAllFieldTypes_ layout(@LayoutRes int arg0) {
     super.layout(arg0);

diff --git a/...elWithAnnotatedClassAndSuperAttributes$SubModelWithAnnotatedClassAndSuperAttributes_.java b/...elWithAnnotatedClassAndSuperAttributes$SubModelWithAnnotatedClassAndSuperAttributes_.java
@@ -1,6 +1,7 @@
 package com.airbnb.epoxy;
 
 import android.support.annotation.LayoutRes;
+import java.lang.CharSequence;
 import java.lang.Object;
 import java.lang.Override;
 import java.lang.String;
@@ -27,6 +28,18 @@ public int superValue() {
     return this;
   }
 
+  @Override
+  public ModelWithAnnotatedClassAndSuperAttributes$SubModelWithAnnotatedClassAndSuperAttributes_ id(CharSequence key) {
+    super.id(key);
+    return this;
+  }
+
+  @Override
+  public ModelWithAnnotatedClassAndSuperAttributes$SubModelWithAnnotatedClassAndSuperAttributes_ id(CharSequence key, long id) {
+    super.id(key, id);
+    return this;
+  }
+
   @Override
   public ModelWithAnnotatedClassAndSuperAttributes$SubModelWithAnnotatedClassAndSuperAttributes_ layout(@LayoutRes int arg0) {
     super.layout(arg0);

diff --git a/epoxy-processortest/src/test/resources/ModelWithAnnotatedClassAndSuperAttributes_.java b/epoxy-processortest/src/test/resources/ModelWithAnnotatedClassAndSuperAttributes_.java
@@ -1,6 +1,7 @@
 package com.airbnb.epoxy;
 
 import android.support.annotation.LayoutRes;
+import java.lang.CharSequence;
 import java.lang.Object;
 import java.lang.Override;
 import java.lang.String;
@@ -27,6 +28,18 @@ public ModelWithAnnotatedClassAndSuperAttributes_ id(long id) {
     return this;
   }
 
+  @Override
+  public ModelWithAnnotatedClassAndSuperAttributes_ id(CharSequence key) {
+    super.id(key);
+    return this;
+  }
+
+  @Override
+  public ModelWithAnnotatedClassAndSuperAttributes_ id(CharSequence key, long id) {
+    super.id(key, id);
+    return this;
+  }
+
   @Override
   public ModelWithAnnotatedClassAndSuperAttributes_ layout(@LayoutRes int arg0) {
     super.layout(arg0);

diff --git a/epoxy-processortest/src/test/resources/ModelWithAnnotatedClass_.java b/epoxy-processortest/src/test/resources/ModelWithAnnotatedClass_.java
@@ -1,6 +1,7 @@
 package com.airbnb.epoxy;
 
 import android.support.annotation.LayoutRes;
+import java.lang.CharSequence;
 import java.lang.Object;
 import java.lang.Override;
 import java.lang.String;
@@ -19,6 +20,18 @@ public ModelWithAnnotatedClass_ id(long id) {
     return this;
   }
 
+  @Override
+  public ModelWithAnnotatedClass_ id(CharSequence key) {
+    super.id(key);
+    return this;
+  }
+
+  @Override
+  public ModelWithAnnotatedClass_ id(CharSequence key, long id) {
+    super.id(key, id);
+    return this;
+  }
+
   @Override
   public ModelWithAnnotatedClass_ layout(@LayoutRes int arg0) {
     super.layout(arg0);

diff --git a/epoxy-processortest/src/test/resources/ModelWithConstructors_.java b/epoxy-processortest/src/test/resources/ModelWithConstructors_.java
@@ -1,6 +1,7 @@
 package com.airbnb.epoxy;
 
 import android.support.annotation.LayoutRes;
+import java.lang.CharSequence;
 import java.lang.Object;
 import java.lang.Override;
 import java.lang.String;
@@ -35,6 +36,18 @@ public ModelWithConstructors_ id(long id) {
     return this;
   }
 
+  @Override
+  public ModelWithConstructors_ id(CharSequence key) {
+    super.id(key);
+    return this;
+  }
+
+  @Override
+  public ModelWithConstructors_ id(CharSequence key, long id) {
+    super.id(key, id);
+    return this;
+  }
+
   @Override
   public ModelWithConstructors_ layout(@LayoutRes int arg0) {
     super.layout(arg0);

diff --git a/epoxy-processortest/src/test/resources/ModelWithFieldAnnotation_.java b/epoxy-processortest/src/test/resources/ModelWithFieldAnnotation_.java
@@ -2,6 +2,7 @@
 
 import android.support.annotation.LayoutRes;
 import android.support.annotation.Nullable;
+import java.lang.CharSequence;
 import java.lang.Object;
 import java.lang.Override;
 import java.lang.String;
@@ -29,6 +30,18 @@ public ModelWithFieldAnnotation_ id(long id) {
     return this;
   }
 
+  @Override
+  public ModelWithFieldAnnotation_ id(CharSequence key) {
+    super.id(key);
+    return this;
+  }
+
+  @Override
+  public ModelWithFieldAnnotation_ id(CharSequence key, long id) {
+    super.id(key, id);
+    return this;
+  }
+
   @Override
   public ModelWithFieldAnnotation_ layout(@LayoutRes int arg0) {
     super.layout(arg0);

diff --git a/epoxy-processortest/src/test/resources/ModelWithFinalField_.java b/epoxy-processortest/src/test/resources/ModelWithFinalField_.java
@@ -1,6 +1,7 @@
 package com.airbnb.epoxy;
 
 import android.support.annotation.LayoutRes;
+import java.lang.CharSequence;
 import java.lang.Object;
 import java.lang.Override;
 import java.lang.String;
@@ -22,6 +23,18 @@ public ModelWithFinalField_ id(long id) {
     return this;
   }
 
+  @Override
+  public ModelWithFinalField_ id(CharSequence key) {
+    super.id(key);
+    return this;
+  }
+
+  @Override
+  public ModelWithFinalField_ id(CharSequence key, long id) {
+    super.id(key, id);
+    return this;
+  }
+
   @Override
   public ModelWithFinalField_ layout(@LayoutRes int arg0) {
     super.layout(arg0);

diff --git a/epoxy-processortest/src/test/resources/ModelWithIntDef_.java b/epoxy-processortest/src/test/resources/ModelWithIntDef_.java
@@ -1,6 +1,7 @@
 package com.airbnb.epoxy.models;
 
 import android.support.annotation.LayoutRes;
+import java.lang.CharSequence;
 import java.lang.Object;
 import java.lang.Override;
 import java.lang.String;
@@ -28,6 +29,18 @@ public ModelWithIntDef_ id(long id) {
     return this;
   }
 
+  @Override
+  public ModelWithIntDef_ id(CharSequence key) {
+    super.id(key);
+    return this;
+  }
+
+  @Override
+  public ModelWithIntDef_ id(CharSequence key, long id) {
+    super.id(key, id);
+    return this;
+  }
+
   @Override
   public ModelWithIntDef_ layout(@LayoutRes int arg0) {
     super.layout(arg0);