Summary of several common Ruby core concepts

Classes and objects in Ruby are important knowledge points. To learn the Ruby language, you must first master the application of Ruby objects and classes. Here we will learn about the Ruby core class.

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Ruby core Class 1, Array

1. instantiation

1) Array. new

2) [value 1, value 2, value 3, value 4, value 5]

3) % w [red green blue balck] automatically converts the string list into an array, saving quotation marks and commas.

2. Method

1) empty? Returns true or false.

2) size returned size

3) first returns the first

4) last returns the last one.

5) delete "element" to delete

3. Tip: view the class help input command ri class name example ri Array

Ruby core Class II. Hash: save key-value pairs

1. instantiation

1) Hash. new

2) {key => value, key => value}

2. Method

1) empty?

2) size

3) keys: returns all keys.

4) values returns all values.

Ruby core Class 3, String: single quotation marks or double quotation marks

1. To include special characters such as quotation marks in a string, escape them"

2. Shortcut: % Q (string) Example: % Q (Arnie said, "I'm back !" )

3. the Ruby expression # {expression} can be embedded in the string. For example, "Current Time: # {Time. now }"

Note that only double quotation marks are supported. single quotation marks output the expressions as they are.

4. Method

Gsub (value 1, value 2), replace value 1 in the string with value 2
Include? (Value) include?
Slice () Interception

Ruby core Class 4: Numeric: Float Fixnum Bignum

1. 123. integer? Integer or not

2. 12.3.round rounding

3. 8. zero? 0 or not

4. 12. Convert to_f to Float

5. Convert 11.3.to _ I to Fixnum.

Ruby core Class 5, Symbol

1. It is equivalent to a string, but there is no method

2. Mutual Conversion

"Fox". to_sym
: Fox. to_s