added property name function to composite index decorator

sample/sample16-indexes/entity/Post.ts

@@ -4,8 +4,10 @@ import {Index} from "../../../src/decorator/indices/Index";
 import {CompositeIndex} from "../../../src/decorator/indices/CompositeIndex";
 
 @Table("sample16_post")
-@CompositeIndex(["title", "text"])
+@CompositeIndex("my_index_with_id_and_text", ["id", "text"])
 @CompositeIndex(["title", "likesCount"])
+@CompositeIndex((post: Post) => [post.title, post.text])
+@CompositeIndex("my_index_with_id_and_title", (post: Post) => [post.id, post.title])
 export class Post {
 
     @PrimaryColumn("int", { generated: true })

src/decorator/indices/CompositeIndex.ts

@@ -6,9 +6,11 @@ import {defaultMetadataStorage} from "../../typeorm";
  */
 export function CompositeIndex(name: string, fields: string[]): Function;
 export function CompositeIndex(fields: string[]): Function;
-export function CompositeIndex(nameOrFields: string|string[], maybeFields?: string[]): Function {
+export function CompositeIndex(fields: (object: any) => any[]): Function;
+export function CompositeIndex(name: string, fields: (object: any) => any[]): Function;
+export function CompositeIndex(nameOrFields: string|string[]|((object: any) => any[]), maybeFields?: ((object: any) => any[])|string[]): Function {
     const name = typeof nameOrFields === "string" ? nameOrFields : undefined;
-    const fields = typeof nameOrFields === "string" ? <string[]> maybeFields : nameOrFields;
+    const fields = typeof nameOrFields === "string" ? <((object: any) => any[])|string[]> maybeFields : nameOrFields;
     
     return function (cls: Function) {
         defaultMetadataStorage().compositeIndexMetadatas.add(new CompositeIndexMetadata(cls, name, fields));

src/metadata/CompositeIndexMetadata.ts

@@ -1,5 +1,6 @@
 import {TargetMetadata} from "./TargetMetadata";
 import {NamingStrategyInterface} from "../naming-strategy/NamingStrategy";
+import {EntityMetadata} from "./EntityMetadata";
 
 /**
  * This metadata interface contains all information about table's composite index.
@@ -15,15 +16,15 @@ export class CompositeIndexMetadata extends TargetMetadata {
      */
     namingStrategy: NamingStrategyInterface;
 
+    /**
+     * Entity metadata of the class to which this index is applied.
+     */
+    entityMetadata: EntityMetadata;
+
     // ---------------------------------------------------------------------
     // Readonly Properties
     // ---------------------------------------------------------------------
 
-    /**
-     * Columns combination to be used as index.
-     */
-    readonly columns: string[];
-
     // ---------------------------------------------------------------------
     // Private Properties
     // ---------------------------------------------------------------------
@@ -33,13 +34,18 @@ export class CompositeIndexMetadata extends TargetMetadata {
      */
     private readonly _name: string;
 
+    /**
+     * Columns combination to be used as index.
+     */
+    private readonly _columns: ((object: any) => any[])|string[];
+
     // ---------------------------------------------------------------------
     // Constructor
     // ---------------------------------------------------------------------
 
-    constructor(target: Function, name: string|undefined, columns: string[]) {
+    constructor(target: Function, name: string|undefined, columns: ((object: any) => any[])|string[]) {
         super(target);
-        this.columns = columns;
+        this._columns = columns;
         if (name)
             this._name = name;
     }
@@ -52,4 +58,15 @@ export class CompositeIndexMetadata extends TargetMetadata {
         return this.namingStrategy.indexName(this.target, this._name, this.columns);
     }
     
+    get columns() {
+        
+        // if columns already an array of string then simply return it
+        if (this._columns instanceof Array)
+            return this._columns;
+
+        // if columns is a function that returns array of field names then execute it and get columns names from it 
+        const propertiesMap = this.entityMetadata.createPropertiesMap();
+        return this._columns(propertiesMap).map((i: any) => String(i));
+    }
+    
 }

src/metadata/EntityMetadata.ts

@@ -38,6 +38,9 @@ export class EntityMetadata {
         // this.indices = indices;
         this.compositeIndices = compositeIndices;
         this.foreignKeys = foreignKeys;
+        
+        // this.relations.forEach(relation => relation.entityMetadata = this);
+        this.compositeIndices.forEach(index => index.entityMetadata = this);
     }
 
     // -------------------------------------------------------------------------