iOS面向过程，面向对象一则实例

//面向过程编程：其中有iOS枚举和结构实例，这段能很好解释iOS中的结构和枚举：

#import <Foundation/Foundation.h>// --------------------------------------------------// constants for the different kinds of shapes and their colorstypedef enum {kCircle,kRectangle,kOblateSpheroid} ShapeType;typedef enum {kRedColor,kGreenColor,kBlueColor} ShapeColor;// --------------------------------------------------// Shape bounding rectangletypedef struct {int x, y, width, height;} ShapeRect;// --------------------------------------------------// The Shapetypedef struct {ShapeType type;ShapeColor fillColor;ShapeRect bounds;} Shape;// --------------------------------------------------// convert from the ShapeColor enum value to a human-readable nameNSString *colorName (ShapeColor colorName){  switch (colorName) {  case kRedColor:      return @"red";      break;  case kGreenColor:      return @"green";      break;  case kBlueColor:      return @"blue";      break;  }  return @"no clue";} // colorNamevoid drawCircle (ShapeRect bounds,  ShapeColor fillColor){NSLog (@"drawing a circle at (%d %d %d %d) in %@",   bounds.x, bounds.y,    bounds.width, bounds.height,   colorName(fillColor));} // drawCirclevoid drawRectangle (ShapeRect bounds, ShapeColor fillColor){NSLog (@"drawing a rectangle at (%d %d %d %d) in %@",   bounds.x, bounds.y,    bounds.width, bounds.height,   colorName(fillColor));} // drawRectanglevoid drawEgg (ShapeRect bounds,   ShapeColor fillColor){NSLog (@"drawing an egg at (%d %d %d %d) in %@",   bounds.x, bounds.y,    bounds.width, bounds.height,   colorName(fillColor));} // drawEgg// --------------------------------------------------// Draw the shapesvoid drawShapes (Shape shapes[], int count){int i;for (i = 0; i < count; i++) {switch (shapes[i].type) {case kCircle:drawCircle (shapes[i].bounds, shapes[i].fillColor);break;case kRectangle:drawRectangle (shapes[i].bounds,    shapes[i].fillColor);break;case kOblateSpheroid:drawEgg (shapes[i].bounds,  shapes[i].fillColor);break;}}} // drawShapes// --------------------------------------------------// The main function.  Make the shapes and draw themint main (int argc, const char * argv[]) {Shape shapes[3];ShapeRect rect0 = { 0, 0, 10, 30 };shapes[0].type = kCircle;shapes[0].fillColor = kRedColor;shapes[0].bounds = rect0;ShapeRect rect1 = { 30, 40, 50, 60 };shapes[1].type = kRectangle;shapes[1].fillColor = kGreenColor;shapes[1].bounds = rect1;ShapeRect rect2 = { 15, 18, 37, 29 };shapes[2].type = kOblateSpheroid;shapes[2].fillColor = kBlueColor;shapes[2].bounds = rect2;drawShapes (shapes, 3);return (0);} // main

面向对象的编程：

#import <Foundation/Foundation.h>// --------------------------------------------------// constants for the different kinds of shapes and their colorstypedef enum {kRedColor,kGreenColor,kBlueColor} ShapeColor;// --------------------------------------------------// Shape bounding rectangletypedef struct {int x, y, width, height;} ShapeRect;// --------------------------------------------------// convert from the ShapeColor enum value to a human-readable nameNSString *colorName (ShapeColor color){NSString *colorName;switch (color) {case kRedColor:colorName = @"red";break;case kGreenColor:colorName = @"green";break;case kBlueColor:colorName = @"blue";break;default:colorName = @"oops! Unexpected color";break;}return (colorName);} // colorName// --------------------------------------------------// Shapes base class@interface Shape : NSObject{ShapeColor  fillColor;ShapeRect   bounds;}- (void) setFillColor: (ShapeColor) fillColor;- (void) setBounds: (ShapeRect) bounds;- (void) draw;@end // Shape@implementation Shape- (void) setFillColor: (ShapeColor) c{fillColor = c;} // setFillColor- (void) setBounds: (ShapeRect) b{bounds = b;} // setBounds- (void) draw{} // draw@end // Shape// --------------------------------------------------// All about Triangles@interface Triangle : Shape@end // Triangle@implementation Triangle- (void) draw{NSLog (@"drawing a triangle at (%d %d %d %d) in %@",   bounds.x, bounds.y,    bounds.width, bounds.height,   colorName(fillColor));} // draw@end // Triangle// --------------------------------------------------// All about Circles@interface Circle : Shape@end // Circle@implementation Circle// I'm new!- (void) setFillColor: (ShapeColor) c{if (c == kRedColor) {c = kGreenColor;}[super setFillColor: c];} // setFillColor- (void) draw{NSLog (@"drawing a circle at (%d %d %d %d) in %@",   bounds.x, bounds.y,    bounds.width, bounds.height,   colorName(fillColor));} // draw@end // Circle// --------------------------------------------------// All about Rectangles@interface Rectangle : Shape@end // Rectangle@implementation Rectangle- (void) draw{NSLog (@"drawing a rectangle at (%d %d %d %d) in %@",   bounds.x, bounds.y,    bounds.width, bounds.height,   colorName(fillColor));} // draw@end // Rectangle// --------------------------------------------------// All about OblateSphereoids@interface OblateSphereoid : Shape@end // OblateSphereoid@implementation OblateSphereoid- (void) draw{NSLog (@"drawing an egg at (%d %d %d %d) in %@",   bounds.x, bounds.y,    bounds.width, bounds.height,   colorName(fillColor));} // draw@end // OblateSphereoid// --------------------------------------------------// Draw the shapesvoid drawShapes (id shapes[], int count){int i;for (i = 0; i < count; i++) {id shape = shapes[i];[shape draw];}} // drawShapes// --------------------------------------------------// The main function.  Make the shapes and draw themint main (int argc, const char * argv[]) {id shapes[4]; // I'm different!ShapeRect rect0 = { 0, 0, 10, 30 };shapes[0] = [Circle new];[shapes[0] setBounds: rect0];[shapes[0] setFillColor: kRedColor];ShapeRect rect1 = { 30, 40, 50, 60 };shapes[1] = [Rectangle new];[shapes[1] setBounds: rect1];[shapes[1] setFillColor: kGreenColor];ShapeRect rect2 = { 15, 19, 37, 29 };shapes[2] = [OblateSphereoid new];[shapes[2] setBounds: rect2];[shapes[2] setFillColor: kBlueColor];ShapeRect rect3 = { 47, 32, 80, 50 };// I'm new!shapes[3] = [Triangle new];[shapes[3] setBounds: rect3];[shapes[3] setFillColor: kRedColor];drawShapes (shapes, 4); // I'm different!return (0);} // main