Swift学习笔记 - 字符串-白红宇

1. 不可变字符串

Objective-C:

NSString *string1 = @"Hello World!";

Swift:

let string1 = "Hello world!"

2. 可变字符串

Objective-C:

NSMutableString *string2 = [NSMutableString new];NSMutableString *string3 = [@"" mutableCopy];

Swift:

var string2 = String()var string3 = ""

3. 输出

Objective-C:

NSLog(@"%lu", (unsigned long)string1.length); // Prints "12"NSLog(@"%i", !string2.length);                 // Prints "1"NSLog(@"%i", [string1 hasPrefix:@"Hello"]); // Prints "1"NSLog(@"%i", [string1 hasSuffix:@"earth!"]);// Prints "0"

Swift:

println(string1.utf16Count)                // Prints "12"println(countElements(string1))            // Prints "12"println(string2.isEmpty)                // Prints "true"println(string1.hasPrefix("Hello"))     // Prints trueprintln(string1.hasSuffix("earth!"))     // Prints false

4. 比较

Objective-C:

// Prints "string2 equals string3"if ([string2 isEqualToString:string3]) {    NSLog(@"string2 equals string3");}

Swift:

// Prints "string2 equals string3"if string2 == string3 {    println("string2 equals string3")}

5. 转换

Objective-C:

NSString *fiveString = [@5 stringValue]; // "5"NSInteger five = [fiveString integerValue];

Swift:

let fiveString = "\(5)"                         // "5"let five = fiveString.toInt()!let pi = Double((π as NSString).doubleValue)     // 3.14

6. Copy and Mutable Copy

Objective-C:

NSMutableString *string4 = [string1 mutableCopy];[string4 appendFormat:@"Am I alone?"];NSLog(@"%@", string1);        // Prints "Hello world!"NSLog(@"%@", string4);        // Prints "Hello world! Am I alone?"NSMutableString *string5 = string4;[string5 replaceCharactersInRange:NSMakeRange(13, 10)    withString:@"How do you like me now"];// Prints "Hello world! How do you like me now?"if ([string4 isEqualToString:string5]) {    NSLog(@"%@", string5);}NSMutableString *tempHigh = [@"85" mutableCopy];NSMutableString *tempLow = [@"70" mutableCopy];NSString *degreeF = @"\u2109";[tempHigh appendString:degreeF];[tempLow appendString:degreeF];// Prints "High/Low: 85°F/70°F"NSLog(@"High/Low: %@/%@", tempHigh, tempLow);

Swift:

var string4 = string1string4 += " Am I alone?"println(string1)         // Prints "Hello world!"println(string4)         // Prints "Hello world! Am I alone?"var string5 = string4let startIndex = advance(string5.startIndex, 13)string5.replaceRange(startIndex..