理解适配器模式

代码示例

Node.js

1// External service (incompatible interface)
2class ThirdPartyBilling {
3  processPayment(cents) {
4    console.log(`ThirdPartyBilling charged ${cents} cents`);
5    return Promise.resolve({ ok: true });
6  }
7}
8
9// Internal service (also incompatible)
10class InternalBilling {
11  chargeUSDollars(dollars) {
12    console.log(`InternalBilling charged $${dollars}`);
13    return { success: true };
14  }
15}
16
17// Adapter interface: standardize to `charge(amountInDollars)`
18class BillingAdapter {
19  constructor(billingClient, type) {
20    this.client = billingClient;
21    this.type = type;
22  }
23
24  async charge(amountInDollars) {
25    if (this.type === 'third-party') {
26      const cents = amountInDollars * 100;
27      const result = await this.client.processPayment(cents);
28      return result.ok;
29    }
30
31    if (this.type === 'internal') {
32      const result = this.client.chargeUSDollars(amountInDollars);
33      return result.success;
34    }
35
36    throw new Error('Unknown billing client');
37  }
38}
39
40// Usage
41async function checkout(amount, adapter) {
42  const ok = await adapter.charge(amount);
43  if (ok) {
44    console.log('Charge succeeded');
45  } else {
46    console.log('Charge failed');
47  }
48}
49
50const thirdParty = new BillingAdapter(new ThirdPartyBilling(), 'third-party');
51const internal = new BillingAdapter(new InternalBilling(), 'internal');
52
53checkout(25, thirdParty);
54checkout(25, internal);

TypeScript

1// External service (incompatible interface)
2class ThirdPartyBilling {
3  processPayment(cents: number): Promise<{ ok: boolean }> {
4    console.log(`ThirdPartyBilling charged ${cents} cents`);
5    return Promise.resolve({ ok: true });
6  }
7}
8
9// Internal service (also incompatible)
10class InternalBilling {
11  chargeUSDollars(dollars: number): { success: boolean } {
12    console.log(`InternalBilling charged $${dollars}`);
13    return { success: true };
14  }
15}
16
17interface BillingClient {
18  charge(amountInDollars: number): Promise<boolean>;
19}
20
21// Adapter interface: standardize to `charge(amountInDollars)`
22class BillingAdapter implements BillingClient {
23  constructor(
24    private client: any,
25    private type: 'third-party' | 'internal'
26  ) {}
27
28  async charge(amount: number): Promise<boolean> {
29    if (this.type === 'third-party') {
30      const cents = amount * 100;
31      const result = await this.client.processPayment(cents);
32      return result.ok;
33    }
34
35    if (this.type === 'internal') {
36      const result = this.client.chargeUSDollars(amount);
37      return result.success;
38    }
39
40    throw new Error('Unknown billing client');
41  }
42}
43
44// Usage
45async function checkout(amount: number, adapter: BillingClient) {
46  const ok = await adapter.charge(amount);
47  console.log(ok ? 'Charge succeeded' : 'Charge failed');
48}
49
50const thirdParty = new BillingAdapter(new ThirdPartyBilling(), 'third-party');
51const internal = new BillingAdapter(new InternalBilling(), 'internal');
52
53checkout(25, thirdParty);
54checkout(25, internal);