colinfwalsh / object-oriented-people-ios-0616

Object Oriented People

Objectives

1. Create a new class that contains read-only properties.
2. Write a designated initializer, default initializer, and convenience initializer to set initial values for the properties of an instance of that class.
3. Write public methods that provide controlled interaction with the read-only properties.

Instructions

Open the object-oriented-people.xcworkspace file.

I. Create the Class Files

Create a new class called FISPerson class that inherits from NSObject.

Declare the Properties

Publicly declare four properties as readonly properties:

• an NSString called name,
• an NSUInteger called ageInYears,
• an NSUInteger called heightInInches, and
• an NSMutableArray called skills.

Top-tip: Remember that primitive-type properties cannot accept a retention attribute (strong or weak).

Insert the private @interface section below the #import statements of the .m implementation file:

//  FISPerson.m

#import "FISPerson.h"

@interface FISPerson ()

@end

@implementation

@end

Top-tip: Don't forget to include the empty parenthesis that conclude the private @interface section.

Now privately redeclare all four properties as readwrite within the private @interface section.

Declare the Methods

Publicly declare the ten following methods in the .h header file:

• init — the default initializer,

• initWithName:ageInYears: — a convenience initializer,

• initWithName:ageInYears:heightInInches: — a designated initializer,

• celebrateBirthday which returns an NSString,

• learnSkillBash which returns void,

• learnSkillXcode which returns void,

• learnSkillObjectiveC which returns void,

• learnSkillObjectOrientedProgramming which returns void,

• learnSkillInterfaceBuilder which returns void, and

• isQualifiedTutor which returns a BOOL.

Define Initial Methods Implementations

Move to the .m implementation file. Utilizing autocomplete to quickly fill in the method name, initially define the methods to:

For the initializers, init, initWithName:ageInYears:, and initWithName:ageInYears:heightInInches:

self = [super init];
return self;

For the celebrateBirthday method:

return nil;

For the five learnSkill... methods, provide no implementation.

For the isQualifiedTutor method:

return NO;

Run the tests with ⌘ U. The build should succeed but the tests should fail. Throughout solving the rest of this lab, run the tests frequently to check your work as you write it.

II. Implement the Initializers

1 — Write the implementation for the designated initializer initWithName:ageInYears:heightInInches:. Remember to follow the designated initializer format that:

• assigns to self a call of [super init],
• checks if (self) {...},
• sets the three properties' instance variables to the associated argument passed into the initializer,
• sets the skills array to an empty NSMutableArray, and
• returns self:

// designated initializer
- (instanceType)initWith... {
    self = [super init];
    if (self) {
        //    ivar        argument
        _propertyName = propertyName;
    }
    return self;
}

2 — Override the default initializer init so that it calls the designated initializer with default arguments that are representations of your own name (i.e. @"Mark") age (i.e. 29) and height (i.e. 71)—now you can brag about being a (data) model! Remember that this method should:

• assign to self a call of the designated initializer upon self, passing in the desired default values as arguments, and
• return self:

// default initializer
- (instancetype)init {
    self = [self initWith...]; // calls designated initializer
    return self;
}

Top-tip: The NSMutableArray ivar should be initialized to an empty NSMutableArray using [[NSMutableArray alloc] init];

3 — Write the implementation for the convenience initializer initWithName:ageInYears:. Remember that this method should:

• assign to self a call of the designated initializer upon self, passing in the arguments for name and ageInYears directly into the designated initializer, and passing in a default value for heightInInches that is reasonable (i.e. 67), and
• return self.

// convenience initializer
-(instancetype)initWith... {
    self = [self initWith...]; // calls designated initializer
    return self;
}

III. Implement the celebrateBirthday Method

1 — Copy the following (private) helper method ordinalForInteger: into the .m implementation file immediately below the empty implementation for celebrateBirthday. This method returns a string containing the correct ordinal for the NSUInteger submitted as the integer argument:

// helper method
- (NSString *)ordinalForInteger:(NSUInteger)integer {
    NSString *ordinal = @"th";
    if (integer % 10 == 1 && integer % 100 != 11) {
        ordinal = @"st";
    } else if (integer % 10 == 2 && integer % 100 != 12) {
        ordinal = @"nd";
    } else if (integer % 10 == 3 && integer % 100 != 13) {
        ordinal = @"rd";
    }
    return ordinal;
}

2 — Write the method implementation for celebrateBirthday to:

• increment the ageInYears property by one:
• capture the return of calling ordinalForInteger: with the self.ageInYears property submitted as the argument:
• use the stringWithFormat: class method on NSString to create a formatted string that will read HAPPY 30TH BIRTHDAY, MARK!!! when an instance of FISPerson with the name property set to @"Mark" and the ageInYears property set to 29 performs the celebrateBirthday method; capture this formatted string into a new string object.
• use an NSLog() to print the birthday message to the console, and
• finally, return the formatted string containing the birthday message so the test can verify it.

IV. Implement the learnSkill... Methods

1 — Write the method implementation for learnSkillBash to check whether the self.skills array already contains the string @"bash", and if not, to add it.

2 — Write the method implementation for learnSkillXcode to check whether the self.skills array already contains the string @"Xcode", and if not, to add it.

3 — Write the method implementation for learnSkillObjectiveC to check whether the self.skills array already contains the string @"Objective-C", and if not, to add it.

4 — Write the method implementation for learnSkillObjectOrientedProgramming to check whether the self.skills array already contains the string @"Object-Oriented Programming", and if not, to add it.

5 — Write the method implementation for learnSkillInterfaceBuilder to check whether the self.skills array already contains the string @"Interface Builder", and if not, to add it.

V. Implement the isQualifiedTutor Method

Write the method implementation for the isQualifiedTutor method. It should check whether there are at least four elements in the self.skills array and:

• if so, it should return YES, but
• if NOT, it should return NO.

Advanced: Ideally this information would be saved in a readonly property with an overridden getter method.

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