(Objective-C) PayPal -- Get an OAuth 2.0 Access Token

Demonstrates how to send a request to get a PayPal OAuth2 access token. Sends an HTTP request equivalent to the following:

curl https://api.sandbox.paypal.com/v1/oauth2/token \
  -H "Accept: application/json" \
  -H "Accept-Language: en_US" \
  -u "Client-Id:Secret" \
  -d "grant_type=client_credentials"

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#import <CkoRest.h>
#import <NSString.h>
#import <CkoJsonObject.h>
#import <CkoDateTime.h>
#import <CkoStringBuilder.h>

// Note: Requires Chilkat v9.5.0.64 or greater.

// This requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

CkoRest *rest = [[CkoRest alloc] init];

// Make the initial connection.
// A single REST object, once connected, can be used for many PayPal REST API calls.
// The auto-reconnect indicates that if the already-established HTTPS connection is closed,
// then it will be automatically re-established as needed.
BOOL bAutoReconnect = YES;
BOOL success = [rest Connect: @"api.sandbox.paypal.com" port: [NSNumber numberWithInt: 443] tls: YES autoReconnect: bAutoReconnect];
if (success != YES) {
    NSLog(@"%@",rest.LastErrorText);
    return;
}

// Duplicate this request:

// 	curl https://api.sandbox.paypal.com/v1/oauth2/token \
// 	  -H "Accept: application/json" \
// 	  -H "Accept-Language: en_US" \
// 	  -u "Client-Id:Secret" \
// 	  -d "grant_type=client_credentials"

[rest AddHeader: @"Accept" value: @"application/json"];
[rest AddHeader: @"Accept-Language" value: @"en_US"];

// For additional help on where to find  your client ID and API secret, see PayPal Client_ID and API_Secret
[rest SetAuthBasic: @"PAYPAL_REST_API_CLIENT_ID" password: @"PAYPAL_REST_API_SECRET"];

[rest AddQueryParam: @"grant_type" value: @"client_credentials"];

NSString *responseStr = [rest FullRequestFormUrlEncoded: @"POST" uriPath: @"/v1/oauth2/token"];
if (rest.LastMethodSuccess != YES) {
    NSLog(@"%@",rest.LastErrorText);
    return;
}

NSLog(@"%@",rest.LastRequestHeader);

// A sample response:

// 	{
// 	  "scope": "https://api.paypal.com/v1/payments/.* https://api.paypal.com/v1/vault/credit-card https://api.paypal.com/v1/vault/credit-card/.*",
// 	  "access_token": "EEwJ6tF9x5WCIZDYzyZGaz6Khbw7raYRIBV_WxVvgmsG",
// 	  "token_type": "Bearer",
// 	  "app_id": "APP-6XR95014BA15863X",
// 	  "expires_in": 28800
// 	}

CkoJsonObject *json = [[CkoJsonObject alloc] init];
[json Load: responseStr];
json.EmitCompact = NO;

// Check the response status code.  A 200 indicates success..
if ([rest.ResponseStatusCode intValue] != 200) {
    NSLog(@"%@",[json Emit]);
    NSLog(@"%@",@"Failed.");
    return;
}

// Given that the access token expires in approx 8 hours,
// let's record the date/time this token was created.
// This will allow us to know beforehand if the token
// is expired (and we can then fetch a new token).
CkoDateTime *dateTime = [[CkoDateTime alloc] init];
BOOL bLocalTime = NO;
int dtNow = [dateTime GetAsUnixTime: bLocalTime];
[json AppendInt: @"tokenCreateTimeUtc" value: [NSNumber numberWithInt: dtNow]];

// Examine the access token and save to a file.
NSLog(@"%@%@",@"Access Token: ",[json StringOf: @"access_token"]);
NSLog(@"%@",@"Full JSON Response:");
NSLog(@"%@",[json Emit]);

CkoStringBuilder *sbResponse = [[CkoStringBuilder alloc] init];
[sbResponse Append: [json Emit]];
BOOL bEmitBom = NO;
[sbResponse WriteFile: @"qa_data/tokens/paypal.json" charset: @"utf-8" emitBom: bEmitBom];