Brian Gesiak | Swift API Design: Getting Results

Presented at www.swiftsummit.com

Transcript

1. share your code
2. share your code
3. Brian Gesiak
 @modocache
5. compelling code
6. 1. Precise 2. Convenient
7. tradeoffs
8. 1. Precise 2. Convenient
10. BananaKit
11. Series
12. Series Z

13. @interface Banana : NSObject /** Whether the banana is peeled. */ @property (readonly) BOOL peeled; /** Whether the banana is delicious. @warning Do not use before the banana is peeled. */ @property (readonly) BOOL delicious; @end
14. @interface Banana : NSObject /** Whether the banana is peeled. */ @property (readonly) BOOL peeled; /** Whether the banana is delicious. @warning Do not use before the banana is peeled. */ @property (readonly) BOOL delicious; @end
15. @interface Banana : NSObject /** Whether the banana is peeled. */ @property (readonly) BOOL peeled; /** Whether the banana is delicious. @warning Do not use before the banana is peeled. */ @property (readonly) BOOL delicious; @end
16. @interface Banana : NSObject /** Whether the banana is peeled. */ @property (readonly) BOOL peeled; /** Whether the banana is delicious. @warning Do not use before the banana is peeled. */ @property (readonly) BOOL delicious; @end
17. BKBanana *banana = [[BKBanana alloc] init]; if (banana.delicious) { // ... }
18. BKBanana *banana = [[BKBanana alloc] init]; if (banana.delicious) { // ... } Caught "NSInternalInconsistencyException" º
19. enum Banana { /** An unpeeled banana has no taste. */ case Unpeeled /** A peeled banana has a boolean to indicate whether it's delicious. */ case Peeled(delicious: Bool) }
20. enum Banana { /** An unpeeled banana has no taste. */ case Unpeeled /** A peeled banana has a boolean to indicate whether it's delicious. */ case Peeled(delicious: Bool) }
21. enum Banana { /** An unpeeled banana has no taste. */ case Unpeeled /** A peeled banana has a boolean to indicate whether it's delicious. */ case Peeled(delicious: Bool) }
22. let banana = Banana.Unpeeled switch banana { case .Unpeeled: // ... case .Peeled(let delicious): if (delicious) { // ... } }
23. let banana = Banana.Unpeeled switch banana { case .Unpeeled: // ... case .Peeled(let delicious): if (delicious) { // ... } }
24. let banana = Banana.Unpeeled switch banana { case .Unpeeled: // ... case .Peeled(let delicious): if (delicious) { // ... } }
25. Banana [[ if } let banana = Banana.Unpeeled switch banana { case .Unpeeled: // ... case .Peeled(let delicious): if (delicious) { // ... } }
26. Banana *banana = [[Banana alloc] init]; if (banana.delicious) { // ... } let switch case case } }
27. MonkeyDB
28. @interface MonkeyDB : NSObject /** Creates a database backed by the store at the given URL. */ - (instancetype)initWithURL:(NSURL *)url; /** Loads a monkey with the given name, or nil if one doesn't exist. */ - (Monkey *)monkeyWithName:(NSString *)name error:(NSError **)error; @end
29. @interface MonkeyDB : NSObject /** Creates a database backed by the store at the given URL. */ - (instancetype)initWithURL:(NSURL *)url; /** Loads a monkey with the given name, or nil if one doesn't exist. */ - (Monkey *)monkeyWithName:(NSString *)name error:(NSError **)error; @end
30. @interface MonkeyDB : NSObject /** Creates a database backed by the store at the given URL. */ - (instancetype)initWithURL:(NSURL *)url; /** Loads a monkey with the given name, or nil if one doesn't exist. */ - (Monkey *)monkeyWithName:(NSString *)name error:(NSError **)error; @end
31. @interface Tricycle : NSObject @property (readonly) NSString *brandName; @end
32. @interface MonkeyDB (Tricycles) /** Looks up whether the given monkey owns a tricycle. If the monkey owns one, returns the tricycle. If not, returns nil. If an error occurs, the error pointer will be populated. */ - (Tricycle *)tricycleForMonkey:(Monkey *)monkey error:(NSError **)error; @end
33. @interface MonkeyDB (Tricycles) /** Looks up whether the given monkey owns a tricycle. If the monkey owns one, returns the tricycle. If not, returns nil. If an error occurs, the error pointer will be populated. */ - (Tricycle *)tricycleForMonkey:(Monkey *)monkey error:(NSError **)error; @end
34. MonkeyDB .monkey(name: String)
35. MonkeyDB .monkey(name: String) MonkeyDB .tricycle(monkey: Monkey)
36. MonkeyDB .monkey(name: String) MonkeyDB .tricycle(monkey: Monkey) Tricycle.brandName
37. NSURL *url = [NSURL fileURLWithPath:@".monkeydb"]; MonkeyDB *database = [[MonkeyDB alloc] initWithURL:url]; NSError *monkeyError = nil; Monkey *monkey = [database monkeyWithName:@"Peepers" error:&monkeyError]; if (monkey == nil || monkeyError != nil) { // ...error handling. return nil; } NSError *tricycleError = nil; Tricycle *tricycle = [database tricycleForMonkey:monkey error:&tricycleError];
38. NSURL *url = [NSURL fileURLWithPath:@".monkeydb"]; MonkeyDB *database = [[MonkeyDB alloc] initWithURL:url]; NSError *monkeyError = nil; Monkey *monkey = [database monkeyWithName:@"Peepers" error:&monkeyError]; if (monkey == nil || monkeyError != nil) { // ...error handling. return nil; } NSError *tricycleError = nil; Tricycle *tricycle = [database tricycleForMonkey:monkey error:&tricycleError];
39. NSURL *url = [NSURL fileURLWithPath:@".monkeydb"]; MonkeyDB *database = [[MonkeyDB alloc] initWithURL:url]; NSError *monkeyError = nil; Monkey *monkey = [database monkeyWithName:@"Peepers" error:&monkeyError]; if (monkey == nil || monkeyError != nil) { // ...error handling. return nil; } NSError *tricycleError = nil; Tricycle *tricycle = [database tricycleForMonkey:monkey error:&tricycleError];
40. NSURL *url = [NSURL fileURLWithPath:@".monkeydb"]; MonkeyDB *database = [[MonkeyDB alloc] initWithURL:url]; NSError *monkeyError = nil; Monkey *monkey = [database monkeyWithName:@"Peepers" error:&monkeyError]; if (monkey == nil || monkeyError != nil) { // ...error handling. return nil; } NSError *tricycleError = nil; Tricycle *tricycle = [database tricycleForMonkey:monkey error:&tricycleError];
41. // ...error handling. return nil; } NSError *tricycleError = nil; Tricycle *tricycle = [database tricycleForMonkey:monkey error:&tricycleError]; if (tricycle == nil || tricycleError != nil) { // ...error handling. return nil; } return tricycle.brandName;
42. // ...error handling. return nil; } NSError *tricycleError = nil; Tricycle *tricycle = [database tricycleForMonkey:monkey error:&tricycleError]; if (tricycle == nil || tricycleError != nil) { // ...error handling. return nil; } return tricycle.brandName;
43. // ...error handling. return nil; } NSError *tricycleError = nil; Tricycle *tricycle = [database tricycleForMonkey:monkey error:&tricycleError]; if (tricycle == nil || tricycleError != nil) { // ...error handling. return nil; } return tricycle.brandName;
44. NSURL *url = [NSURL fileURLWithPath:@".monkeydb"]; MonkeyDB *database = [[MonkeyDB alloc] initWithURL:url]; Monkey *monkey = [database monkeyWithName:@"Peepers" error:nil]; Tricycle *tricycle = [database tricycleForMonkey:monkey error:nil]; return tricycle.brandName;
45. NSURL *url = [NSURL fileURLWithPath:@".monkeydb"]; MonkeyDB *database = [[MonkeyDB alloc] initWithURL:url]; Monkey *monkey = [database monkeyWithName:@"Peepers" error:nil]; Tricycle *tricycle = [database tricycleForMonkey:monkey error:nil]; return tricycle.brandName; Caught "NSInternalInconsisntencyException" º
46. NSURL *url = [NSURL fileURLWithPath:@".monkeydb"]; MonkeyDB *database = [[MonkeyDB alloc] initWithURL:url]; Monkey *monkey = [database monkeyWithName:@"Peepers" error:nil]; Tricycle *tricycle = [database tricycleForMonkey:monkey error:nil]; return tricycle.brandName; Thread 1: EXC_BAD_INSTRUCTION
47. if (brandName) {
 // ...
 }
48. /** The result of an operation that could have failed. */ enum Result<SuccessType, ErrorType> { /** If the operation succeeded, the result has a value. */ case Success(SuccessType) /** If the operation failed, the result holds an error. */ case Failure(ErrorType) }
49. /** The result of an operation that could have failed. */ enum Result<SuccessType, ErrorType> { /** If the operation succeeded, the result has a value. */ case Success(SuccessType) /** If the operation failed, the result holds an error. */ case Failure(ErrorType) }
50. /** The result of an operation that could have failed. */ enum Result<SuccessType, ErrorType> { /** If the operation succeeded, the result has a value. */ case Success(SuccessType) /** If the operation failed, the result holds an error. */ case Failure(ErrorType) }
51. LlamaKit
52. LlamaKit github.com/LlamaKit
53. struct MonkeyDB { init(url: NSURL) func monkey(name: String) -> Result<Monkey, NSError> func tricycle(monkey: Monkey) -> Result<Tricycle, NSError> }
54. struct MonkeyDB { init(url: NSURL) func monkey(name: String) -> Result<Monkey, NSError> func tricycle(monkey: Monkey) -> Result<Tricycle, NSError> }
55. struct MonkeyDB { init(url: NSURL) func monkey(name: String) -> Result<Monkey, NSError> func tricycle(monkey: Monkey) -> Result<Tricycle, NSError> }
56. let result = database.tricycle(monkey) return result.brandName
57. let result = database.tricycle(monkey) return result.brandName 'Result<Tricycle, NSError>' does not have a member named 'brandName' 
58. let monkeyResult = database.monkey(“Peepers") switch monkeyResult { case .Failure(let error): return .Failure(error) case .Success(let monkey): let tricycleResult = database.tricycle(monkey) switch tricycleResult { case .Failure(let error): return .Failure(error) case .Success(let tricycle): return .Success(tricycle.brandName) } }
59. let monkeyResult = database.monkey(“Peepers") switch monkeyResult { case .Failure(let error): return .Failure(error) case .Success(let monkey): let tricycleResult = database.tricycle(monkey) switch tricycleResult { case .Failure(let error): return .Failure(error) case .Success(let tricycle): return .Success(tricycle.brandName) } }
60. let monkeyResult = database.monkey(“Peepers") switch monkeyResult { case .Failure(let error): return .Failure(error) case .Success(let monkey): let tricycleResult = database.tricycle(monkey) switch tricycleResult { case .Failure(let error): return .Failure(error) case .Success(let tricycle): return .Success(tricycle.brandName) } }
61. let monkeyResult = database.monkey(“Peepers") switch monkeyResult { case .Failure(let error): return .Failure(error) case .Success(let monkey): let tricycleResult = database.tricycle(monkey) switch tricycleResult { case .Failure(let error): return .Failure(error) case .Success(let tricycle): return .Success(tricycle.brandName) } }
62. let monkeyResult = database.monkey(“Peepers") switch monkeyResult { case .Failure(let error): return .Failure(error) case .Success(let monkey): let tricycleResult = database.tricycle(monkey) switch tricycleResult { case .Failure(let error): return .Failure(error) case .Success(let tricycle): return .Success(tricycle.brandName) } }
63. 1. Precise 2. Convenient
64. let monkeyResult = database.monkey(“Peepers") switch monkeyResult { case .Failure(let error): return .Failure(error) case .Success(let monkey): let tricycleResult = database.tricycle(monkey) switch tricycleResult { case .Failure(let error): return .Failure(error) case .Success(let tricycle): return .Success(tricycle.brandName) } }
65. MonkeyDB .monkey(name: return MonkeyDB .tricycle(monkey: return
66. MonkeyDB .monkey(name: return .Failure(NSError) MonkeyDB .tricycle(monkey: return .Success( Tricycle.brandName)
67. MonkeyDB .monkey(name: String) return .Failure(NSError) MonkeyDB .tricycle(monkey: return .Success( Tricycle.brandName)
68. MonkeyDB .monkey(name: String) return .Failure(NSError) MonkeyDB .tricycle(monkey: return .Success( Tricycle.brandName)
69. MonkeyDB .monkey(name: String) return .Failure(NSError) MonkeyDB .tricycle(monkey: Monkey) return .Success( Tricycle.brandName)
70. MonkeyDB .monkey(name: String) return .Failure(NSError) MonkeyDB .tricycle(monkey: Monkey) return .Success( Tricycle.brandName)
71. MonkeyDB .monkey(name: String) return .Failure(NSError) MonkeyDB .tricycle(monkey: Monkey) return .Success( Tricycle.brandName)
72. MonkeyDB .monkey(name: return MonkeyDB .tricycle(monkey: return
73. MonkeyDB .monkey(name: return MonkeyDB .tricycle(monkey: return
74. MonkeyDB .monkey(name: return MonkeyDB .tricycle(monkey: return
75. enum Result<SuccessType, ErrorType> { func map<NewType>(transform: SuccessType -> NewType) -> Result<NewType, ErrorType> func flatMap<NewType>( transform: SuccessType -> Result<NewType, ErrorType>) -> Result<NewType, ErrorType> }
76. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult
77. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult
78. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult
79. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult
80. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult
81. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult
82. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult
83. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult
84. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult
85. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult
86. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult
87. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult
88. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult
89. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult
90. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult
91. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult
92. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult
93. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult let tricycleResult = monkeyResult.flatMap { return database.tricycle($0) }
94. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { (monkey: Monkey) in return database.tricycle(monkey) } let brandNameResult = tricycleResult.map { (tricycle: Tricycle) in return tricycle.brandName } return brandNameResult let tricycleResult = monkeyResult.flatMap { return database.tricycle($0) } let brandNameResult = tricycleResult.map { return $0.brandName }
95. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { return database.tricycle($0) } let brandNameResult = tricycleResult.map { return $0.brandName } return brandNameResult
96. let monkeyResult = database.monkey("Peepers") let tricycleResult = monkeyResult.flatMap { return database.tricycle($0) } let brandNameResult = tricycleResult.map { return $0.brandName } return brandNameResult let brandNameResult = tricycleResult.map { $0.brandName } let tricycleResult = monkeyResult.flatMap { database.tricycle($0) }
97. return database.monkey("Peepers") .flatMap { database.tricycle($0) } .map { $0.brandName }
98. return database.monkey("Peepers") .flatMap { database.tricycle($0) } .map { $0.brandName }
99. return database.monkey("Peepers") .flatMap { database.tricycle($0) } .map { $0.brandName }
100. return database.monkey("Peepers") .flatMap { database.tricycle($0) } .map { $0.brandName }
104. Gift
105. Gift https://github.com/modocache/Gift
106. let url = NSURL( fileURLWithPath: "/Users/modocache/Gift")! let latestCommitMessage = openRepository(url) .flatMap { $0.headReference } .flatMap { $0.commit } .flatMap { $0.message } switch latestCommitMessage { case .Success(let message): println(message) case .Failure(let error): println(error.localizedDescription) }
107. let url = NSURL( fileURLWithPath: "/Users/modocache/Gift")! let latestCommitMessage = openRepository(url) .flatMap { $0.headReference } .flatMap { $0.commit } .flatMap { $0.message } switch latestCommitMessage { case .Success(let message): println(message) case .Failure(let error): println(error.localizedDescription) }
108. let url = NSURL( fileURLWithPath: "/Users/modocache/Gift")! let latestCommitMessage = openRepository(url) .flatMap { $0.headReference } .flatMap { $0.commit } .flatMap { $0.message } switch latestCommitMessage { case .Success(let message): println(message) case .Failure(let error): println(error.localizedDescription) }
109. let url = NSURL( fileURLWithPath: "/Users/modocache/Gift")! let latestCommitMessage = openRepository(url) .flatMap { $0.headReference } .flatMap { $0.commit } .flatMap { $0.message } switch latestCommitMessage { case .Success(let message): println(message) case .Failure(let error): println(error.localizedDescription) }
110. let url = NSURL( fileURLWithPath: "/Users/modocache/Gift")! let latestCommitMessage = openRepository(url) .flatMap { $0.headReference } .flatMap { $0.commit } .flatMap { $0.message } switch latestCommitMessage { case .Success(let message): println(message) case .Failure(let error): println(error.localizedDescription) }
111. openRepository(url) .flatMap { $0.index } .flatMap { $0.add() } .flatMap { $0.writeTree() } .flatMap { $0.commit("This is bananas!") } git commit --all --message "this is bananas"
112. openRepository(url) .flatMap { $0.index } .flatMap { $0.add() } .flatMap { $0.writeTree() } .flatMap { $0.commit("This is bananas!") } git commit --all --message "this is bananas"
113. openRepository(url) .flatMap { $0.index } .flatMap { $0.add() } .flatMap { $0.writeTree() } .flatMap { $0.commit("This is bananas!") } git commit --all --message "this is bananas"
114. openRepository(url) .flatMap { $0.index } .flatMap { $0.add() } .flatMap { $0.writeTree() } .flatMap { $0.commit("This is bananas!") } git commit --all --message "this is bananas"
115. openRepository(url) .flatMap { $0.index } .flatMap { $0.add() } .flatMap { $0.writeTree() } .flatMap { $0.commit("This is bananas!") } git commit --all --message "this is bananas"
116. let entryCountResult = openRepository(url) .flatMap { $0.index } .map { $0.entryCount } git status --staged | wc -l
117. let entryCountResult = openRepository(url) .flatMap { $0.index } .map { $0.entryCount } git status --staged | wc -l
118. let entryCountResult = openRepository(url) .flatMap { $0.index } .map { $0.entryCount } git status --staged | wc -l
119. let entryCountResult = openRepository(url) .flatMap { $0.index } .map { $0.entryCount } git status --staged | wc -l
120. let entryCountResult = openRepository(url) .flatMap { $0.index } .map { $0.entryCount } git status --staged | wc -l
121. let entryCountResult = openRepository(url) .flatMap { $0.index } .map { $0.entryCount } git status --staged | wc -l
122. let entryCountResult = openRepository(url) .flatMap { $0.index } .map { $0.entryCount } git status --staged | wc -l
123. enum Result<SuccessType, ErrorType> { func map<NewType>(transform: SuccessType -> NewType) -> Result<NewType, ErrorType> func flatMap<NewType>( transform: SuccessType -> Result<NewType, ErrorType>) -> Result<NewType, ErrorType> }
124. enum Result<SuccessType, ErrorType> { func map<NewType>(transform: SuccessType -> NewType) -> Result<NewType, ErrorType> func flatMap<NewType>( transform: SuccessType -> Result<NewType, ErrorType>) -> Result<NewType, ErrorType> }
125. enum Result<SuccessType, ErrorType> { func map<NewType>(transform: SuccessType -> NewType) -> Result<NewType, ErrorType> func flatMap<NewType>( transform: SuccessType -> Result<NewType, ErrorType>) -> Result<NewType, ErrorType> }
126. enum Result<SuccessType, ErrorType> { func map<NewType>(transform: SuccessType -> NewType) -> Result<NewType, ErrorType> func flatMap<NewType>( transform: SuccessType -> Result<NewType, ErrorType>) -> Result<NewType, ErrorType> }
127. enum Result<SuccessType, ErrorType> { func map<NewType>(transform: SuccessType -> NewType) -> Result<NewType, ErrorType> func flatMap<NewType>( transform: SuccessType -> Result<NewType, ErrorType>) -> Result<NewType, ErrorType> }
128. enum Result<SuccessType, ErrorType> { func map<NewType>(transform: SuccessType -> NewType) -> Result<NewType, ErrorType> func flatMap<NewType>( transform: SuccessType -> Result<NewType, ErrorType>) -> Result<NewType, ErrorType> }
129. enum Result<SuccessType, ErrorType> { func map<NewType>(transform: SuccessType -> NewType) -> Result<NewType, ErrorType> func flatMap<NewType>( transform: SuccessType -> Result<NewType, ErrorType>) -> Result<NewType, ErrorType> }
130. let entryCountResult = openRepository(url) .flatMap { $0.index } .map { $0.entryCount } git status --staged | wc -l
131. tradeoff?
132. return database.monkey("Peepers") .flatMap { database.tricycle($0) } .map { $0.brandName }
133. 1. Precise 2. Convenient
134. Thanks!
135. Thanks!
136. @modocache
 github.com/LlamaKit/LlamaKit github.com/modocache/Gift github.com/SwiftGit2/SwiftGit2