*If we want to talk about wishes in the future,we use:
-I wish (I/we) could+inf.
-I wish (he/she/it/you /they) would+inf.
EX:I wish I could be rich in the future.(I am poor now)
EX:I wish they would stop talking.(The are talking aloud)
EX:I wish we could travel to London.I like London.
*If we want to talk about wishes in the present,we use:
-I wish+subject+past simple.
EX:I wish I had money now.I don't have money now.
EX:I wish he didn't come with us.He went with them.
EX:I wish It were very cold.It is hot now.
using were instead of was is acceptable with all pronouns but we may use was with its pronouns(I/he /she/it):
EX:I wish It was very cold.
*If we want to talk about wishes in the past,we use:
-I wish+subject+past perfect.
-In this use ,we express regrets about what we did or didn't so we can't change any thing.
EX:I wish I had studied hard.He didn't study so he failed the exam.
EX:I wish I hadn't spent much money last week.I regretted spending a lot of money.
*Note:(If only) is used to talk about regrets like wish either in the present or in the past:
EX:If only I hadn't spent a lot of money.I spent alot.
EX:If only I were free.I am busy.