Convert to custom BUYAssert. Will throw exception in release builds.

Mobile Buy SDK/Mobile Buy SDK.xcodeproj/project.pbxproj

@@ -414,6 +414,8 @@
 		9A47CF0D1CE4D6C600A6D5BA /* BUYCreditCardTokenTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 9A47CF0C1CE4D6C600A6D5BA /* BUYCreditCardTokenTests.m */; };
 		9A47CF0F1CE4D7A800A6D5BA /* BUYApplePayTokenTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 9A47CF0E1CE4D7A800A6D5BA /* BUYApplePayTokenTests.m */; };
 		9A47CF201CE50EBB00A6D5BA /* BUYApplePayTestToken.m in Sources */ = {isa = PBXBuildFile; fileRef = 9A47CF1F1CE50EBB00A6D5BA /* BUYApplePayTestToken.m */; };
+		9A47CF221CE5112A00A6D5BA /* BUYAssert.h in Headers */ = {isa = PBXBuildFile; fileRef = 9A47CF211CE5112A00A6D5BA /* BUYAssert.h */; };
+		9A47CF231CE5112A00A6D5BA /* BUYAssert.h in Headers */ = {isa = PBXBuildFile; fileRef = 9A47CF211CE5112A00A6D5BA /* BUYAssert.h */; };
 		9A6B03791CDA5D4F0054C26E /* BUYAccountCredentialsTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 9A6B03781CDA5D4F0054C26E /* BUYAccountCredentialsTests.m */; };
 		BE10079B1B6165EC0031CEE7 /* BUYOptionValueCell.h in Headers */ = {isa = PBXBuildFile; fileRef = BE1007991B6165EC0031CEE7 /* BUYOptionValueCell.h */; };
 		BE10079C1B6165EC0031CEE7 /* BUYOptionValueCell.m in Sources */ = {isa = PBXBuildFile; fileRef = BE10079A1B6165EC0031CEE7 /* BUYOptionValueCell.m */; };
@@ -759,6 +761,7 @@
 		9A47CF0E1CE4D7A800A6D5BA /* BUYApplePayTokenTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = BUYApplePayTokenTests.m; sourceTree = "<group>"; };
 		9A47CF1E1CE50EBB00A6D5BA /* BUYApplePayTestToken.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = BUYApplePayTestToken.h; sourceTree = "<group>"; };
 		9A47CF1F1CE50EBB00A6D5BA /* BUYApplePayTestToken.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = BUYApplePayTestToken.m; sourceTree = "<group>"; };
+		9A47CF211CE5112A00A6D5BA /* BUYAssert.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = BUYAssert.h; path = ../Additions/BUYAssert.h; sourceTree = "<group>"; };
 		9A6B03781CDA5D4F0054C26E /* BUYAccountCredentialsTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = BUYAccountCredentialsTests.m; sourceTree = "<group>"; };
 		BE1007991B6165EC0031CEE7 /* BUYOptionValueCell.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = BUYOptionValueCell.h; sourceTree = "<group>"; };
 		BE10079A1B6165EC0031CEE7 /* BUYOptionValueCell.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = BUYOptionValueCell.m; sourceTree = "<group>"; };
@@ -1282,6 +1285,7 @@
 		F773744519C779C20039681C /* Utils */ = {
 			isa = PBXGroup;
 			children = (
+				9A47CF211CE5112A00A6D5BA /* BUYAssert.h */,
 				F70CE40D1A8BF1D90055BEB8 /* BUYApplePayAdditions.h */,
 				F70CE40E1A8BF1D90055BEB8 /* BUYApplePayAdditions.m */,
 				BE33B4ED1B15FF4D0067982B /* BUYApplePayHelpers.h */,
@@ -1368,6 +1372,7 @@
 				84DD12AD1CC63FE600A2442D /* _BUYProductVariant.h in Headers */,
 				84980F2A1CB75AC200CFAB58 /* BUYObjectProtocol.h in Headers */,
 				901931281BC5B9BC00D1134E /* BUYApplePayHelpers.h in Headers */,
+				9A47CF231CE5112A00A6D5BA /* BUYAssert.h in Headers */,
 				901931291BC5B9BC00D1134E /* BUYStoreViewController.h in Headers */,
 				9019312A1BC5B9BC00D1134E /* BUYCreditCard.h in Headers */,
 				9019312B1BC5B9BC00D1134E /* BUYOption.h in Headers */,
@@ -1485,6 +1490,7 @@
 				84DD128B1CC63FE600A2442D /* _BUYLineItem.h in Headers */,
 				84980F291CB75AC200CFAB58 /* BUYObjectProtocol.h in Headers */,
 				BE9A64741B503D2E0033E558 /* BUYApplePayHelpers.h in Headers */,
+				9A47CF221CE5112A00A6D5BA /* BUYAssert.h in Headers */,
 				BE9A647E1B503D930033E558 /* BUYStoreViewController.h in Headers */,
 				BE9A64551B503CC50033E558 /* BUYCreditCard.h in Headers */,
 				BE9A645F1B503CE90033E558 /* BUYOption.h in Headers */,

Mobile Buy SDK/Mobile Buy SDK/Additions/BUYAssert.h

+//
+//  BUYAssert.h
+//  Mobile Buy SDK
+//
+//  Created by Dima Bart on 2016-05-12.
+//  Copyright © 2016 Shopify Inc. All rights reserved.
+//
+
+#define BUYAssert(exp, ...) \
+do { \
+	if (!(exp)) { \
+		@throw [NSException exceptionWithName:NSInternalInconsistencyException reason:[NSString stringWithFormat:__VA_ARGS__] userInfo:nil]; \
+	} \
+} while(0)

Mobile Buy SDK/Mobile Buy SDK/Data/BUYClient.m

@@ -26,6 +26,7 @@
 
 #import "BUYClient_Internal.h"
 
+#import "BUYAssert.h"
 #import "BUYAddress.h"
 #import "BUYCart.h"
 #import "BUYCheckout.h"
@@ -55,7 +56,7 @@
 #define kMinSuccessfulStatusCode 200
 #define kMaxSuccessfulStatusCode 299
 
-#define BUYAssertCheckout(checkout) NSAssert([(checkout) hasToken], @"Checkout assertion failed. Checkout must have a valid token associated with it.")
+#define BUYAssertCheckout(checkout) BUYAssert([(checkout) hasToken], @"Checkout assertion failed. Checkout must have a valid token associated with it.")
 
 NSString * const BUYVersionString = @"1.3";