From 24c531b90370cd87bc346fce550092d13ae53e35 Mon Sep 17 00:00:00 2001
From: pearmini <subairui@icloud.com>
Date: Sat, 8 May 2021 20:28:38 +0800
Subject: [PATCH] feat(constant): add getTicks

---
 __tests__/unit/scales/constant.spec.ts | 35 ++++++++++++++++++++++++--
 docs/scales/constant.md                |  6 +++++
 src/scales/constant.ts                 | 11 ++++++++
 src/types.ts                           |  2 +-
 4 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/__tests__/unit/scales/constant.spec.ts b/__tests__/unit/scales/constant.spec.ts
index 7e592d6a..0efbcc7a 100644
--- a/__tests__/unit/scales/constant.spec.ts
+++ b/__tests__/unit/scales/constant.spec.ts
@@ -1,12 +1,15 @@
-import { Constant, ConstantOptions } from '../../../src';
+import { Constant, ConstantOptions, d3Ticks } from '../../../src';
 
 describe('Constant', () => {
   test('Constant() has expected defaults', () => {
     const s = new Constant();
-    expect(s.getOptions()).toEqual({
+    const { tickMethod, ...options } = s.getOptions();
+    expect(options).toEqual({
       range: [0],
       domain: [0, 1],
+      tickCount: 5,
     });
+    expect(tickMethod).toBe(d3Ticks);
   });
 
   test('Constant(options) override defaults', () => {
@@ -73,6 +76,34 @@ describe('Constant', () => {
     expect(s.getOptions()).toEqual(s1.getOptions());
   });
 
+  test('getTicks() returns desired ticks', () => {
+    const s = new Constant({
+      tickMethod: (a, b, n) => {
+        expect(a).toBe(0);
+        expect(b).toBe(1);
+        expect(n).toBe(n);
+        return [a, b];
+      },
+    });
+
+    expect(s.getTicks()).toEqual([0, 1]);
+
+    s.update({
+      domain: [1, 'a'],
+    });
+    expect(s.getTicks()).toEqual([]);
+
+    s.update({
+      domain: ['a', 1],
+    });
+    expect(s.getTicks()).toEqual([]);
+
+    s.update({
+      domain: ['a', 'b'],
+    });
+    expect(s.getTicks()).toEqual([]);
+  });
+
   test('clone() returns a scale isolating change with the original one', () => {
     const s = new Constant();
     const s1 = s.clone();
diff --git a/docs/scales/constant.md b/docs/scales/constant.md
index c38b6993..8be6809e 100644
--- a/docs/scales/constant.md
+++ b/docs/scales/constant.md
@@ -30,6 +30,8 @@ x.invert('2'); // [0, 10]
 | domain | Sets the scale’s domain to the specified array of values. | <code>number[] &#124; string[]</code> | `[0, 1]` |
 | range | Sets the scale’s range to the specified array of values. | `number[]` | `[0]` |
 | unknown | Sets the output value of the scale for `undefined` (or `NaN`) input values. | `any` | `undefined` |
+| tickCount | Sets approximately count representative values from the scale’s domain. | `number` | `5` |
+| tickMethod | Sets the method for computing representative values from the scale’s domain. | `(options?: ConstantOptions) => number[]` | r-pretty|
 
 ## Methods
 
@@ -52,3 +54,7 @@ Returns the scale's current options.
 <a name="constant_clone" href="#constant_clone">#</a> **clone**<i>(): Constant</i>
 
 Returns a new constant scale with the independent and same options as the original one.
+
+<a name="constant_getTicks" href="#constant_getTicks">#</a> **getTicks**<i>(): number[]</i>
+
+Returns representative values from the scale’s domain computed by specified `options.tickMethod` with `options.tickCount` if options.domain are numbers, otherwise `[]`.
diff --git a/src/scales/constant.ts b/src/scales/constant.ts
index 0438f546..e4cddb23 100644
--- a/src/scales/constant.ts
+++ b/src/scales/constant.ts
@@ -1,3 +1,5 @@
+import { isNumber } from '@antv/util';
+import { d3Ticks } from '../tick-methods/d3-ticks';
 import { ConstantOptions, Domain, Range } from '../types';
 import { Base } from './base';
 
@@ -11,6 +13,8 @@ export class Constant extends Base<ConstantOptions> {
       range: [0],
       domain: [0, 1],
       unknown: undefined,
+      tickCount: 5,
+      tickMethod: d3Ticks,
     };
   }
 
@@ -35,6 +39,13 @@ export class Constant extends Base<ConstantOptions> {
     return x === v && v !== undefined ? this.options.domain : [];
   }
 
+  public getTicks() {
+    const { tickMethod, domain, tickCount } = this.options;
+    const [a, b] = domain;
+    if (!isNumber(a) || !isNumber(b)) return [];
+    return tickMethod(a, b, tickCount);
+  }
+
   /**
    * 克隆 Constant Scale
    * @returns 拥有相同选项且独立的 Constant Scale
diff --git a/src/types.ts b/src/types.ts
index e97c2924..58b00599 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -48,7 +48,7 @@ export type Unknown<O extends BaseOptions> = O['unknown'];
 export type IdentityOptions = BaseOptions<number> & TickOptions;
 
 /** Constant 比例尺的选项 */
-export type ConstantOptions = BaseOptions<number | string>;
+export type ConstantOptions = BaseOptions<number | string> & TickOptions;
 
 /** Continuous 比例尺的选项 */
 export type ContinuousOptions<D = any, R = D> = BaseOptions<D, R> &